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Electroanalytical Methods for theDetermination of Pharmaceuticals:A Review of Recent Trends andDevelopmentsBengi Uslu a & Sibel A. Ozkan aa Faculty of Pharmacy, Department of Analytical Chemistry, AnkaraUniversity, Tandogan-Ankara, Turkey
Available online: 28 Oct 2011
To cite this article: Bengi Uslu & Sibel A. Ozkan (2011): Electroanalytical Methods for theDetermination of Pharmaceuticals: A Review of Recent Trends and Developments, Analytical Letters,44:16, 2644-2702
To link to this article: http://dx.doi.org/10.1080/00032719.2011.553010
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Electrochemistry
ELECTROANALYTICAL METHODS FOR THEDETERMINATION OF PHARMACEUTICALS: AREVIEW OF RECENT TRENDS AND DEVELOPMENTS
Bengi Uslu and Sibel A. OzkanFaculty of Pharmacy, Department of Analytical Chemistry, AnkaraUniversity, Tandogan-Ankara, Turkey
Electroanalysis is a powerful analytical technique that is increasing in utility in the
pharmaceutical industry. It is used as an alternative or complementary technique to spectro-
photometric and separation techniques due to its high sensitivity, speed of analysis, reduction
in solvent and sample consumption, and low operating cost compared to other analytical
methods. A review of the principles and application of modern electroanalytical techniques,
namely, cyclic, linear sweep, differential pulse, square wave and stripping voltammetric tech-
niques, is presented. This review gives recent pharmaceutical analysis applications used for
each mode of electroanalytical chemistry. The review will also describe recent developments
for enhancing concentration limits of detection, electrode types, and so forth. Selected
studies on these subjects are given as examples.
Keywords: Cyclic voltammetry; Electroanalysis; Pharmaceutical products; Pulse techniques; Stripping
techniques
INTRODUCTION
During the past years, there has been extraordinary acceleration of progress inthe discovery, synthesis, sensitive analysis, and means of delivery of pharmaceuti-cally active compounds used in the diagnosis, prevention, and treatment of humandiseases. Analyses of smaller amounts of biological samples such as blood, serum,urine, and so forth, are often requested hence required determination methods musthave low detection and determination limits and should be applicable to smallsamples. Electrochemical techniques are powerful and versatile analytical techniquesthat offer high sensitivity, accuracy, and precision as well as large linear dynamicrange, with relatively low-cost instrumentation. After developing more sensitivepulse methods, the electroanalytical studies are more regularly used on the druganalysis in their dosage forms and especially in biological samples. However, electro-analytical techniques can easily solve many problems of pharmaceutical interest with
Received 22 September 2010; accepted 3 December 2010.
Address correspondence to Sibel A. Ozkan, Faculty of Pharmacy, Department of Analytical
Chemistry, Ankara University, 06100, Tandogan-Ankara, Turkey. E-mail: [email protected]
Analytical Letters, 44: 2644–2702, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0003-2719 print=1532-236X online
DOI: 10.1080/00032719.2011.553010
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a high degree of accuracy, precision, sensitivity, and selectivity employing thisapproach. Some of the most useful electroanalytical techniques are based on theconcept of continuously changing the applied potentials to the electrode-solutioninterface and the resulting measured current (Kissinger and Heineman 1996; J. Wang2006; Smyth and Vos 1992; Ozkan, Uslu, and Aboul-Enein 2003; Bard and Faulkner2001; Kellner et al. 2004; Hart 1990). Most of the pharmaceutical active compoundswere found to be as electrochemically active.
The voltammetric methods used today in analytical chemistry laboratories weremade possible by recent advances in instrumentation, computerized processing ofanalytical data, and in particular, innovative electrochemists. The term working elec-trode is reserved for the electrode at which the reaction of interest occurs. Solid ormercury-based electrodes are used as working electrodes in voltammetric techniques.In general, solid electrode materials have the advantage of being more mechanicallystable, and they provide a larger anodic range than mercury-based electrodes. Also,the handling of solid electrodes is much easier such that they may readily be appliedin flow streams due to their mechanical stability and hardness (Uslu and Ozkan2007a, 2007b; J. Wang et al. 1999; Brainina and Neyman 1993; J. Wang 1988; Harvey2000; Bond 1980; Adams 1969).
The field of modified solid electrodes has become very popular with a largenumber of applications in industry, quality control of drugs and food, determinationin pharmaceutical dosage forms, environmental monitoring, and so forth. Thepotential range over which voltammetric techniques can be used depends on the solidelectrode material, the solvent, the supporting electrolyte, and pH of the studiedsolution. Solid electrode voltammetry is used largely for the oxidation of substancesat fairly positive potentials as well as for very easily reproducible substances. The per-formance of the voltammetric procedure is strongly influenced by the material of theworking electrode (Uslu and Ozkan 2007a, 2007b; J. Wang et al. 1999; J. Wang 1988;Harvey 2000; Bond 1980; Adams 1969).
Some of the most useful electroanalytical techniques are based on the conceptof continuously changing the applied potentials to the electrode-solution interfaceand the resulting measured current. The most commonly used voltammetric methodsare cyclic (CV), linear sweep (LSV), normal pulse (NPV), differential pulse (DPV),square wave (SWV), and stripping voltammetry (Kissinger and Heineman 1996; J.Wang 2006; Smyth and Vos 1992; Ozkan et al. 2003; Bard and Faulkner 2001;Kellner et al. 2004; J. Wang et al. 1999; Brainina and Neyman 1993; J. Wang1988; Harvey 2000; Gosser 1988; Koryta, Dvorak, and Kavan 1993; Bagotsky2006; Zoski 2007; Greef et al. 1990; Nicholson, 1965; Kissinger and Heineman 1983).
Modern electrochemical methods are sensitive, selective, rapid, and easy techni-ques applicable to analysis in the pharmaceutical fields and, indeed, in most areas ofanalytical chemistry, especially compared with the classical methods. As a generalrule, many of the drug active compounds can be readily oxidized or reduced incontrast to the excipients of pharmaceutical dosage forms. Electrochemical measure-ments are two-dimensional, with the potential related to qualitative properties andthe current related to quantitative properties. Thus, compounds can be selectivelydetected by electrochemical methods. This selectivity depends on the accessible poten-tial range, the number of compounds that are active in this range, and on the half-width of the single signals. The advantages of electrochemical methods are the ease
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of sample preparation and lack of interferences from excipients in the pharmaceuticaldosage forms (Kissinger and Heineman 1996; J. Wang 2006; Smyth and Vos 1992;Bard and Faulkner 2001; J. Wang 1988; Zoski 2007; Greef et al. 1990; Barker andJenkin 1952).
In addition to the analytical aspect, electrochemistry allows the establishmentof the electrochemical behavior of a given drug through mechanistic studies. In somecases, there is a relationship between voltammetry and drugs, and the knowledge ofthe mechanism of their electrode reactions can give a useful clue in elucidation of themechanism of their interaction with living cells and their fate in the human bodyafter administration as the dosage form. This is of particular interest with respectto the pharmacological knowledge of the drug. Electrochemical techniques are mostsuitable to investigate the redox properties of a new drug; this can give insights intoits metabolic fate (Kissinger and Heineman 1996; J. Wang 2006; Smyth and Vos1992; Ozkan et al. 2003; Kellner et al. 2004; Hart 1990).
The purpose of this review is to give the basic information about electroanaly-tical methods, working electrodes, and their applications on pharmaceutically activecompounds in their dosage forms and in biological fluids. An attempt was made tochoose only application on drug compounds and readily available publicationsdescribing some advances in methodology and applications. The extent of this reviewmakes it impossible to quote all papers dealing with various polarographic andespecially the voltammetric determination of drugs. Thus, only selected examplesdemonstrating the applicability in biological media and=or in dosage forms of theelectroanalytical methods for various classes of drugs are presented.
CYCLIC AND LINEAR SWEEP VOLTAMMETRY
Two voltammetric techniques, LSV and CV, are the most effective and com-monly used electrochemical techniques for studying redox reactions of pharmaceu-tical active compounds. These are the most widely used for acquiring qualitativeinformation about electrochemical reactions. These techniques are not sensitiveenough for trace amount determination of pharmaceutical compounds but it is use-ful to optimize analytical conditions and it gives some important information aboutthe oxidation=reduction mechanism of drug compounds. The LSV and CV methodsalso powerful tool for the rapid determination of formal potentials, detection ofchemical reactions that precede or follow electron transfer or evaluation of electrontransfer kinetics. Both techniques require simple and inexpensive instrumentationand provide not only information on the electrochemical quantities typical of redoxprocess, but also allow investigations of chemical reactions coupled with chargetransfer step. For both techniques, a simple potential wave form that is used oftenin electrochemical experiments is the linear wave form, that is, the potential is con-tinuously changed as a linear function of time. The rate of change of potential withtime is referred to as the scan rate (Kissinger and Heineman 1996; J. Wang 2006;Smyth and Vos 1992; Ozkan et al. 2003; Kellner et al. 2004; J. Wang 1988; Harvey2000; Gosser 1988; Koryta et al. 1993; Zoski 2007; Brainina and Neyman 1993;Adams 1969; Bard and Faulkner 2001; Hart 1990).
The CV method has become a very popular technique for initial electrochemi-cal studies of new systems and has proven very useful in obtaining information about
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fairly complicated electrode reactions. Especially, the CV curves give someinformation about electron transfer kinetics and thermodynamics as well as theconsequences of electron transfer. The CV method is a potentially controlled electro-chemical experiment in which the direction of the potential is reversed at the end ofthe first scan. Thus, the waveform is usually of the form of an isosceles triangle. Thissweep is described in general by its initial, high, final potentials, and scan rate. TheCV method is the most widely used technique for acquiring qualitative informationabout electrochemical reactions. The important parameters of CV scan are themagnitude of the peak current and the peak potentials. A redox couple in which bothspecies are stable and rapidly exchange electrons with the working electrode istermed an electrochemically reversible couple. The peak current obtained at a planarelectrode for a reversible process is described by Randles-Sevcik equation (forT¼ 298� K):
Ip ¼ 2; 69� 105 n3=2 A:D1=2Cn1=2
where Ip is the peak current (Amperes); n is the number of electrons (equivalent=mol); n is the potential scan rate (V=sec); A and D are the electrode area (cm2)and the diffusion coefficient (cm2=sec), respectively; and C is the analyte concen-tration (mol=L). According to this equation, the peak current is directly proportionalto concentration and increases with the square root of the scan rate. A redox couplein which both species are stable and rapidly exchange electrons with the workingelectrode is termed an electrochemically reversible couple. The number of electronstransferred during the electrode reaction for a reversible couple can be determinedfrom the separation between the anodic and cathodic peak potentials at about0.059V=n (Kissinger and Heineman 1996; J. Wang 2006; Smyth and Vos 1992; Bardand Faulkner 2001; Kellner et al. 2004; J. Wang et al. 1999; Brainina and Neyman1993; Zoski 2007; Nicholson 1965; Kissinger and Heineman 1983; Hart 1990).
In practice, the three parameters that need to be characterized are the startingpotential of the scan, the finishing potential and the scan rate in cyclic voltammetricmeasurements. An electrochemical process occurs frequently through a sequence ofsteps including:
1. The charge transfer reaction;2. The transfer of the reactant from the solution to the electrode surface and the
product from the electrode surface to the solution; and3. Possible oxidation or reduction mechanisms of the analyte and possible chemical
reactions preceding, following or the charge transfer step.
Additionally, adsorption or other surface reactions may need to be investigated.It is often the first experiment performed in an electrochemical study of a
compound, a biological material, or an electrode surface. Accordingly, the techniquehas been used widely in studying the redox mechanism of many biologically signifi-cant molecules. The result of such investigations into the redox mechanism ofdrugs may have profound effects on understanding of their in vivo redox processesof pharmaceutical activity.
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The LSV method involves monitoring current as a function of appliedpotential when a regularly varying potential is applied to the working electrode.When scanning linearly across a series of potentials, the observed current is a func-tion of potential and time. The potential limits that can be applied depend on thereference electrode, the working electrode material, and the nature and the compo-sition of the supporting electrolyte. In LSV, the potential of the working is rampedfrom an initial potential to a final potential. The potential of the working electrode ischanged linearly with time. The solution is unstirred and linear diffusion is main-tained in this technique. The scan rate direction can be signed for showing the poten-tial scan direction as negative for cathodic sweep and positive for anodic sweep. Withthis technique, the peak current is proportional to scan rate and large signals areobtained with very fast scans. The LSV method is a very useful electroanalyticaltechnique with most solid electrodes because rapid analysis times can be achievedwith about 10�6M detection limit (Kissinger and Heineman 1996; J. Wang 2006;Smyth and Vos 1992; Ozkan et al. 2003; Bard and Faulkner 2001). The maximumcurrent is called peak current and the corresponding potential is called peak poten-tial. Peak potential gives the qualitative information of the investigated compound.Also, peak current or peak height gives the quantitative amount of the compounds.
In both LSV and CV, a small stationary working electrode is dipped in anunstirred solution containing an excess of supporting electrolyte to repress migrationof charged reactants and products, so that any transfer of electroactive species to andfrom the electrode surface can occur only through diffusion. The LSV and CV meth-ods involve the application of a rapid linear potential sweep, usually between 10 and1000mVs�1. They are very useful techniques at solid electrodes as rapid analysis timescan be achieved. Also, more complicated reactions and irreversible or reversible reac-tions have been examined using the CV technique. The sweep interval can include thewhole potential range of interest, that is, for aqueous supporting electrolytes fromabout þ1.40V to �0.20V vs. Ag=AgCl electrode or be limited to shorter or longerintervals of interest and depending on working electrodes.
Analytical applications of CV and LSV can be realized using the peak current(intensity) and concentration correlation. The CV and LSV methods with inherentdetection limits of about 10�6M, are generally not sensitive enough to determinedrugs in body fluids after therapeutic doses. Actually, quantitative determinationsare usually performed solely by LSV as they are based on the response height; as aresult, no additional information is provided by CV. Both methods are well suitedfor analytical studies devoted to the rapid, simple, and accurate determination ofdrugs in raw materials, pharmaceuticals, or in biological samples. Examples of CVand LSV determination of pharmaceutically active include many classes of drugs:antibiotics, diuretics, antineoplastics, muscle relaxants, neuroleptics, analgesics,vitamins, hormones, and others. Some selected analytical data on the CV and LSVdetermination of organic compounds in pharmaceutical preparations and biologicalmedia are listed in Table 1.
Pulse Techniques
In pulse methods, the procedures are based on the application of pulse changesof potential, and the current response is measured at a suitable time relative to the
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Table
1.SelectedexamplesofCV
andLSV
techniques
onpharm
aceuticalcompoundsin
theirdosageform
sandbiologicalmedia
Compounds
Electrochem
ical
behavior
Working
electrode
Usingmethod
LOD
orLOQ
value
Applicationmedia
References
Nifedipine
Oxidationand
Reduction
GC
CV
andLSV
8�10�5M
and
2�10�5M
Tablets
andcapsules
Senturk,Ozkan,and
Ozkan1998
Indomethacine
Reduction
HMDE
CV
10ng�m
L�1
Dosage
form
;Urine;
Plasm
a
Ali1999
Tetracycline,
Chlortetracycline,
Oxytetracycline
Reduction
HgFilm
Electrode
CV
7�10�7M,
7�10�7M,
1.5�10�6M
Raw
material
Zhouet
al.1999
Nitrofurazone
Reduction
HMDE
LSV
1�10�9M
Ointm
ent;Urine;
Serum
Khodari,Mansour,
andMersal1999
Prazosin
Reduction
Nafioncoated
CPE
CV
andLSV
—Voltammetric
behavior
Arranzet
al.1999
Buprenorphine
Oxidation
CPE
CV
2�10�7M
VialsandTab
lets
Garcia-Fernan
dez
etal.1999
ThiopentoneNa
Reduction
HMDE
LSV
1�10�8M
Dosage
form
;Urine;
Serum
Ali,Farghaly,and
Ghandour2000
Phenothiazines
(Promazine;
promethazine;
levopromazine)
Oxidation
CPE;Glass-like
carbon
LSV
2.5�10�5M;
2.5�10�5M;
6.2�10�5M
Dosage
form
sSandulescuet
al.2000
Zuclopenthixol
Oxidation
GC
CV
andLSV
—Voltammetric
behavior
Senturk
etal.2000
Ascorbic
acid
Oxidation
SPCE
CV
—Voltammetric
Behavior
Florouet
al.2000
Thiram
Oxidation
Aumicrodisc
CV
4.3�10�7M
Dosage
form
sHernandez-O
lmos
etal.2000
Tacrine
Oxidation
CPE
CV
—Voltammetric
behavior
Aparicioet
al.2000
(Continued
)
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Table
1.Continued
Compounds
Electrochem
ical
behavior
Working
electrode
Usingmethod
LOD
orLOQ
value
Applicationmedia
References
Cefepim
eReduction
HMDE
CV
—Voltammetric
behavior
Jimenez
Palacioset
al.
2000
Buprenorphine
Oxidation
CPE
CV
—Voltammetric
behavior
Angeles
Garcia
etal.
2000
Ketoconazole
Oxidation
Pt,Au,GC
CV
—Voltammetric
behavior
Shamsipurand
Farhad
i2000
Albendazole
Oxidation
GC
LSV
3.0�10�5M
Tablets
DeOliveira
and
Stradiotto2001
Gallamine
triethiodide
Reduction
HMDE
LSV
3�10�9M
Ampoules
Ali,Ghandour,and
Abd-ElFattah2001
Isosorbidedinitrate
Reduction
Au
LSV
0.08mg
mL�1
Dosage
form
;
Arterialplasm
a;
Synthetic
serum
Parham
andZargar
2001
Lan
soprazol
Reduction
HMDE
CV
—Voltammetric
behavior
Yardım
cıandOzaltın
2001
Etodolac
Oxidation
GC
CV
andLSV
—Voltammetric
behavior
Yılmaz,
Uslu,and
Ozkan2001
a-tocopherol
Oxidation
CPE
CV
—Voltammetric
behavior
Jaiswa,Ijeri,and
Srivastava2001
OlsalazineNa
Oxidation
GC
CV
andLSV
—Voltammetric
behavior
Uslu,Yılmaz,
and
Ozkan2001
Sertraline
Reduction
HMDE
CV
andLSV
—Voltammetric
behavior
Velaet
al.2001
Melatonin
and
Pyridoxine
Oxidation
GC
CV
—Voltammetric
behavior
Uslu,Dem
ircigil,et
al.
2001
Captopril
Reduction
HMDE
LSV
0.019ngmL�1
Dosage
form
;Urine;
Serum
Ghandouret
al.2002
Ascorbic
acid
Oxidation
Modified
Al
electrode
LSV
2�10�6M
Fresh
fruitjuice;
Dosage
form
s;
plasm
a
Pournaghi-Azar,
Razm
i-Nerbin,and
Hafezi
2002
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Ascorbic
acid
Electrocatalytic
oxidation
Polymer
modified
micro
electrode
LSV
1�10�4M
Dosage
form
Lupuet
al.2002
Colchicine
Reduction
HMDE
CV
1nM
Dosage
form
s;
Biologicalmedia
Kasim
2002
Nalidixic
Acid
Reduction
HMDE
CV
0.766ng�m
L�1
Dosage
form
s;
Biologicalmedia
Ibrahim
,Shehatta,
andSultan2002
Meloxicam
Reduction
SMDE
CV
—Voltammetric
behavior
Altinoz,
Nem
utlu,and
Kir2002
Vitam
inP
Reduction
HMDE
CV
2�10�9M
Tablets
Song,He,
andGuo
2002
FluvastatineNa
Oxidation
GC
CV
—Voltammetric
behavior
OzkanandUslu2002
Acetaminophen
Oxidation
BDD
thin
film
electrode
CV
10mM
Syrup
Wangfuengkanagu
l
andChailapakul
2002
S-A
denosyl-L-
Methionine
Oxidation
GC
CV
andLSV
—Voltammetric
behavior
Uslu,Ozkan,and
Aboul-Enein2002
Alfuzosine
Oxidation
GC
CV
andLSV
—Voltammetric
behavior
Uslu2002
Nitrofurantoin
Reduction
HMDE
CV
—Voltammetric
behavior
Hammam
2002
Acrivastine
Reduction
HgElectrode
CV
—Voltammetric
behavior
Fernandez
Torres
etal.
2002
Praziquantel
Reduction
HMDE
CV
—Voltammetric
behavior
M.M.Ghoneim,
Mabrouk,and
Tawfik2002
5-A
mino-salicylic
acid
Oxidation
GC
LSV
—Voltammetric
behavior
Nigovic
andSim
unic
2003a
Ambroxol
Oxidation
GC
CV
—Voltammetric
behavior
Dem
ircigilet
al.2003
Piribedil
Oxidation
GC
CV
andLSV
—Voltammetric
behavior
UsluandOzkan2003
Melatonin
Oxidation
CPE
CV
3�10�8M
Dosage
form
sCorujo-A
ntunaet
al.
2003
(Continued
)
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Table
1.Continued
Compounds
Electrochem
ical
behavior
Working
electrode
Usingmethod
LOD
orLOQ
value
Applicationmedia
References
Azithromycin
Oxidation
GC
CV
andLSV
—Voltammetric
behavior
Nigovic
andSim
unic
2003b
Hydrochloroquine
Reduction
GC
CV
—Voltammetric
behavior
Arguelho,Andrade,
andStradiotto2003
Sparfloxacin
Reduction
b-cyclodextrin
modified
CPE
CV
—Voltammetric
behavior
Reddy,Sreedhar,and
Reddy2003
PyridoxineHCl
(Vitamin
B6)
Oxidation
Modified
CPE
CV
1.2�10�6M
Dosage
form
sTeixeira
etal.2003
Ascorbic
acid
Oxidation
Modified
CPE
CV
6.3�10�5M
Dosage
form
sRaoof,Ojani,and
Hosseinzadeh
2003
Naproxen
Oxidation
Pt
CV
andLSV
—Voltammetric
behavior
Adhoum
etal.2003
Tiopronin
Oxidation
DiamondFilm
Electrode
CV
50mM
Dosage
form
sSiangproh,
Wangfuengk
anagu
l,
andChailapakul
2003
Tetracycline
Oxidation
Rotatinggold
discelectrode
CV
—Voltammetric
behavior
Palaharn
etal.2003
Fenofibrate
Reduction
HMDE
CV
—Voltammetric
behavior
Yardım
cıandOzaltın
2004
Chlordiazepoxide
Reduction
HgElectrode
CV
—Voltammetric
behavior
El-Hefnawey
etal.
2004
Amisulpride
Oxidation
GC
CV
—Voltammetric
behavior
Ozkan,Uslu,and
Senturk
2004
Salicylicacid
Oxidation
GC
CV
—Voltammetric
behavior
Torriero
etal.2004
Azithromycin
Oxidation
CPE
CV
—Voltammetric
behavior
Farghaly
and
Mohamed
2004
Amiloride
Reduction
HMDE
CV
—Voltammetric
behavior
Hammam
2004.
PyridoxineHCl
Oxidation
Modified
CPE
CV
andLSV
—Voltammetric
behavior
Teixeira,Marino,
etal.2004
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Rifampicineand
Isoniazid
Oxidation
CPE
CV
—Voltammetric
behavior
Hammam,Beltagi,
andGhoneim
2004
Warfarin
Reduction
HMDE
CV
—Voltammetric
behavior
M.M.Ghoneim
and
Tawfik2004
Imatinib
Reduction
HMDE
CV
—Voltammetric
behavior
Hammam,El-Desoky,
Tawfik,et
al.2004
Isoprenaline
Oxidation
Modified
CPE
CV
8�10�5M
Dosageform
sBonifacioet
al.2004
AcetylsalicylicAcid
Oxidation
Enzymeelectrode
CV
Antioxidant
capacity
measured
Dosageform
sCampanella
etal.2004
Ciprofloxacin;
Azithromycin
Oxidatio
Paraffin
impregnated
graphite
electrode
CV
Qualitative
determination
Dosageform
sKomorsky-Lovricand
Nigovic
2004
Abacavir
Oxidation
GC
CV
—Voltammetric
behavior
UsluandOzkan2004
Dipyrone
Oxidation
Modified
CPE
CV
7.2�10�6M
Dosageform
sTeixeira,Marcolino,
etal.2004
Nifuroxazide
Oxidation
GC
CV
—Decomposition
product
of
nifuroxazide
Toralet
al.2004
Levonorgestrel
Reduction
HMDE
CV
—Voltammetric
behavior
M.M.Ghoneim
etal.
2004
CetirizineHCl
Oxidation
GC
CV
—Voltammetric
behavior
Gungor2004
Bromocriptine
Oxidation
GC
LSV
0.01mg
mL�1
Tab
lets
A.Radi,El-Shahawi,
andElm
ogy2005
TriprolidineHCl
Reduction
HMDE
LSV
2.64ngmL�1
Dosageform
sZayed
andHabib
2005
Tobramycine
Reduction
HMDE
LSV
3.44�10�9M
Dosageform
s;
Urine;
Serum
N.Sunet
al.2005
Trimethoprim
Reduction
HMDE
LSV
1�10�7M
Suspensiondosage
form
Carapuca,Cabral,and
Rocha2005
Aminoacid
Oxidation
ScreenPrinted
Electrode
LSV
5�10�5M
Dietary
Solution
Vasjariet
al.2005
(Continued
)
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Table
1.Continued
Compounds
Electrochem
ical
behavior
Working
electrode
Usingmethod
LOD
orLOQ
value
Applicationmedia
References
Zafi
rlukast
Reduction
GC
andHMDE
LSV
—Voltammetric
behavior
SusluandAltinoz
2005
Cefixim
eOxidation
GC
LSV
—Voltammetric
behavior
Golcu,Dogan,and
Ozkan2005
Carvedilol
Oxidation
GC
LSV
—Voltammetric
behavior
DoganandOzkan
2005
Metoclopramide
Oxidation
Audiscmicro
electrode
CV
3.0pg�m
L�1
Dosage
form
sNorouzi,Ganjali,and
Matloobi2005
Ganciclovir
Oxidation
GC
CV
—Voltammetric
behavior
Uslu,DoganTopal,
andOzkan2005
Naproxen
Oxidation
BDDE
CV
—Voltammetric
behavior
Suryanarayananet
al.
2005
Guaifenesin
Oxidation
Pt
CV
—Voltammetric
behavior
Tapsoba,Belgaied,
andBoujlel
2005
Salbutamol
Oxidation
Audiscmicro
electrode
CV
2�10�9M
Dosage
form
s;
Biologicalsamples
Ganjaliet
al.2005
Haloperidol
Reduction
HMDE
CV
—Voltammetric
behavior
El-Desokyand
Ghoneim
2005
Captopril
Oxidation
Modified
CPE
CV
—Voltammetric
behavior
Shahrokhianet
al.
2005
Lam
ivudine
Reduction
HMDE
CV
—Voltammetric
behavior
Dogan,Uslu,et
al.
2005
Quetiapine
Oxidation
GC
LSV
—Voltammetric
behavior
Ozkan,Uslu,and
Dogan2006
N-acetylcysteine
Oxidation
CPE
LSV
6.3�10�5M
Dosage
form
sToitoSuarezet
al.
2006
Amoxicillin
Oxidation
Modified
CPE
LSV
24.8mM
Tablets
Bergaminiet
al.2006
Ceftiofur
Reduction
HMDE
LSV
6.0�10�10M
Dosage
form
s;
Bovineserum
Jacques
Barbosa
etal.
2006
Donepezil
Oxidation
GC
LSV
—Voltammetric
behavior
GolcuandOzkan2006
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Ascorbic
acid
Oxidation
GC
LSV
—Voltammetric
behavior
Erdurak-K
ilic
etal.
2006
Valacyclovir
Oxidation
GC
CV
—Voltammetric
behavior
Uslu,Ozkan,and
Senturk
2006
Imipramine
Oxidation
Aumicro
electrode
LSV
14pgmL�1
Dosageform
Norouzi,Ganjali,and
Akbari-A
dergani
2006
Quetiapine
Oxidation
GC
CV
—Voltammetric
behavior
Ozkanet
al.2006
Sim
vastatin
Oxidation
GC
CV
—Voltammetric
behavior
CoruhandOzkan
2006
Ascorbic
acid
Oxidation
Modified
CPE
CV
2.9�10�5M
Dosageform
sRaoofet
al.2006
Danazol
Reduction
HMDE
CV
—Voltammetric
behavior
Alghamdi,Belal,and
Al-Omar2006
Pyrantelpamoate
Reduction
GC
CV
—Voltammetric
behavior
Jain,Jadon,and
Radhap
yari2006
Meloxicam
Oxidation
GC
LSV
0.02mM
Dosageform
s;
Urine;
Plasm
a
Farhadiand
Karimpour2007
Ethinylestradiol
Oxidation
CPE
LSV
3.0�10�8M
Tab
lets
Li2007
Tryptophan
Oxidation
Multi-walled
carbon
nanotube
modified
CPE
LSV
—Voltammetric
behavior
Shahrokhianand
Fotouhi2007
Ticlopidine
Reduction
HMDE
CV
—Voltammetric
behavior
TurkozandOnar2007
Resveratrol
Oxidation
CPE
CV
—Voltammetric
behavior
H.Zhang,Xu,and
Zheng2007
Glipizide
Reduction
HMDE
CV
—Voltammetric
behavior
E.M.Ghoneim
etal.
2007
Verap
amil
Oxidation
GC
CV
—Voltammetric
behavior
Dem
ircan,Kir,and
Ozkan2007
Ranitidine
Oxidation
Audisc
micro
electrode
CV
25pgmL�1
Dosageform
sNorouzi,Ganjali,and
Daneshgar2007
Lidocaine
Oxidation
BDDE
CV
—Voltammetric
behavior
Oliveira
etal.2007
(Continued
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Table
1.Continued
Compounds
Electrochem
ical
behavior
Working
electrode
Usingmethod
LOD
orLOQ
value
Applicationmedia
References
Nabumetone
Oxidation
GC
CV
—Voltammetric
behavior
Altunet
al.2007
NaltrexoneHCl
Oxidation
Audisc
micro
electrode
CV
andLSV
8�10�4M
Tablets
Norouzi,Ganjali,
Zare,et
al.2007
D-Penicillamine
Oxidation
Modified
CPE
CV
6.04�10�4M
Capsules
Raoof,Ojani,and
Chekin
2007
L-C
ysteine
Oxidation
Modified
CPE
CV
2.0�10�6M
Tablets,
Aminoplasm
a
Serum
Raoof,Ojani,and
Beitollahi2007
Amfepramone
Reduction
HMDE
CV
—Voltammetric
behavior
DeCarvalhoet
al.
2007
Phenothiazines
Oxidation
GC
CV
1.0�10�6M
Humanbodyfluids
EnsafiandHeydari
2008
Bergenin
Oxidation
MWCNTCPE
CV
7.0�10�8M
Dosage
form
sZhuanget
al.2008
Cefdinir
Reduction
HMDE
CV
0.3�10�6M
Dosage
form
sJain,Dwivedit,and
Mishra
2008
Pentoxifylline
Oxidation
GC
CV
—Voltammetric
behavior
Hedgeand
Nandibew
oor2008
Isoniazid
Oxidation
Modified
GC
CV
1.0�10�8M
Dosage
form
sG.Yanget
al.2008
Viloxazine
Oxidation
GC
CV
—Voltammetric
behavior
Garridoet
al.2008
Leucine
Oxidation
MWCNT
modified
GC
CV
3.0�10�6M
Biologicalsamples
RezaeiandZare
2008a
Noscap
ine
Oxidation
MWCNT
modified
GC
CV
8.0�10�8M
Blood;Dosage
form
sRezaeiandZare
2008b
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PromethazineHCl
Oxidation
BDDE
CV
—Voltammetric
behavior
Ribeiro
etal.2008
Furosemide
Oxidation
Graphite
polyurethane
composite
electrode
CV
21mM
Dosage
form
sSem
aanet
al.2008
Nalidixic
Acid
Oxidation
Audisc
microelectrode
CV
0.07pgmL�1
Dosage
form
sNorouzi
etal.2008
Spironolactone
Reduction
HMDE
LSV
1.72�10�10M
Dosage
form
s;
Urine;
Serum
A.H.Al-Ghamdi
etal.2008
Opipramol
Oxidation
GC
LSV
—Voltammetric
behavior
TurhanandUslu2008
Cinnarizine
Reduction
GC
LSV
9�10�9M
Dosage
form
s;
Serum
El-Sayed
etal.2008
Pefloxacin
Oxidation
GC;BDDE
LSV
—Voltammetric
behavior
Usluet
al.2008
Methim
azole
Oxidation
Modified
CPE
LSV
—Voltammetric
behavior
Shahrokhianand
Ghalkhania
2008
Sertindole
Oxidation
GC;BDDE
LSV
—Voltammetric
behavior
Altunet
al.2009
Methotrexate
Oxidation
Modified
GC
CV
—Voltammetric
behavior
F.Wanget
al.2009
DrotaverineHCl
Reduction
HMDE
CV
—Voltammetric
behavior
Zayed
andIssa
2009
Abbreviations:
GC:glassycarbon;HMDE:Hangingmercury
dropelectrode;
CV:Cyclic
voltammetry;LSV:Linearsw
eepvoltam
metry;CPE:CarbonPaste
electrode;
SPCE:Screenprintedcarbonelectrode;
SMDE:Staticmercury
dropelectrode;
BDDE:Boron-deped
diamondelectrode;
MWCNT
CPE:Multiwalled
carbonnanotubes
carbonpasteelectrode.
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time of the pulse. Pulse technique was proposed by Barker and Gardner (1960) inorder to improve the polarographic performance and to lower the detection limitsfor electroactive species. The basis of all pulse techniques is the difference in the rateof the decay of the charging and the faradaic currents following a potential step orpulse. The charging current decays exponentially, whereas the faradaic current (for adiffusion-controlled current) decays as a function of 1=1
ffiffiffiffiffiffiffiffiffi
timep
, that is, the rate ofdecay of the charging current is considerably faster than the decay of the faradaiccurrent (Barker and Gardner 1960; Hamann, Hamnett, and Vielstich 2007). Pulsetechniques improve detection limits as they benefit from the different variation ofdiffusion and capacitive current intensities with time; when carrying out measure-ments at the pulse end, the capacitive current is practicably negligible, the value ofthe faradaic currents still being significant (Kissinger and Heineman 1996; J. Wang2006; Smyth and Vos 1992; Ozkan et al. 2003; Bard and Faulkner 2001; Kellner et al.2004; J. Wang et al. 1999; Brainina and Neyman 1993; J. Wang 1988; Harvey 2000;Gosser 1988; Koryta et al. 1993; Bagotsky 2006; Zoski 2007; Greef et al. 1990). Bysubstantially increasing the ratio between the faradaic and non-faradaic currents,pulse techniques permit convenient limit of quantitation at about 10�8M concen-tration level. The pulsed type of sampling has the advantage of an increase in sensi-tivity and better characteristics for analytical applications.
The pulse amplitude, pulse width, sample period and for some pulse techni-ques, pulse period or drop time are the important parameters of pulse techniques.Pulsed waveforms are more complex and these can be divided primarily into normalpulse, differential pulse (DPV) and square wave (SWV), voltammetry=polarography.The main weakness of pulse analysis, common to most electroanalytical techniques,is a limited ability to resolve complex systems. DP and SW have been mostly appliedpulse waveform in electrochemical drug analysis. These techniques have beenextremely useful for the determination of low amounts of electroactive compoundsin pharmaceuticals, tissues, and biological fluids. Consequently, some selected appli-cations on drug analysis which are obtained using DP and SW pulse waveform aregiven in this review.
Differential Pulse Polarography/Voltammetry (DPV)
DP is an extremely useful technique for measuring trace levels of pharmaceu-tically active compounds. The excitation waveform is basically the staircase. In DPtechnique, fixed-magnitude pulses superimposed on a linear potential ramp areapplied to the working electrode at a time just before the end of the drop. The cur-rent is sampled twice in each pulse period that once before the pulse and the secondsampling is done at the end of the pulse. The difference between these two currentvalues as a function of the potential is recorded and displayed (Barker and Gardner1960). The application of these pulses allows for discrimination of the unwantedcapacity current from the required faradaic current. When the electrode employedis a DME, the technique is called as DPP. When solid electrodes are employed thetechnique is known as DPV. DP technique is one of the most sensitive voltammetrictechniques because the charging currents are strongly discriminated and the ratio offaradaic to charging current is large (Hamann et al. 2007). Differential pulse curvesare peak shaped and thus are well suited to analytical purposes.
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Due to its high sensitivity, DP method is particularly useful for trace analysis,e.g., for drug active compounds, forensic or environmental science. Because of theseadvantages and the availability of low-cost instruments, DPV is often the choice forthe determination of drug active compounds in their dosage forms and in bodyfluids. The greatest advantage of DP method is increased sensitivity, allowing lowvalue of LOD of various compounds. Several applications, based primarily on theDME and solid electrode are given in Table 2.
Square-Wave Voltammetry/Polarography (SWV)
SWV is a powerful electrochemical technique that can be applied in electroana-lytical measurements (Barker and Gardner 1960; Ozkan 2009; O’Dea, Osteryoung,and Osteryoung 1981). SWV is a large amplitude differential technique in which awaveform composed of a symmetrical square wave, superimposed on a staircase,is applied to the working electrode. The current is sampled twice during eachsquare-wave cycle, once at the end of the forward pulse, and once at the end ofthe reverse pulse. The difference between the two measurements is plotted vs. thestaircase potential. The resulting peak-shaped voltammogram displays excellent sen-sitivity and effective discrimination against background contributions (Mirceski,Komorsky-Lovric, and Lovric 2007). The SW techniques can be divided three basicgroups: the Barker, Kalusek, and Osteryoung formats. The most common form ofSW techniques is Osteryoung SWV technique.
The advantage of SWV is that a response can be found at a high effective scanrate, thus reducing the scan time. Because of this advantage, SWV is employed moreoften than other pulse techniques. There are advantages: greater speed in analysisand lower consumption of electroactive species in relation to DPV, and reducedproblems with blocking of the electrode surface. SWV is similar to DPV in that cur-rent is samples at two different times in the waveform and results in a differentialoutput. The forward current is measured at just before the down pulse is applied.The reverse current is measured at the end of the reverse pulse. The currents are mea-sured during the last few microseconds of each pulse and the difference between thecurrent measured on two successive as a net response. The net current is defined fromdifferences between forward and reverse current. The sensitivity increases from thefact that the net current is larger than either the forward or reverse components.The resulting voltammogram is peak-shaped and symmetric about the half-wavepotential. Also the sensitivity of SWV is mostly higher than that of DPV.
SWV provides several advantages to the electroanalyst. First, the applicationof the SWV waveform is that the detrimental effects of charging current are reducedand so the scan rate can be increased drastically. The second advantage of SWV isoxygen need not be excluded from the analyte solution; provided the voltammetricpeak is more cathodic than that for the reduction of oxygen, then the magnitudeof both forward and reverse current will incorporate an equal current due to thereduction of oxygen. The other advantage of SWV, the difference of currents islarger than either forward or reverse current, so the height of the peak is usuallyquite easy to read, thus increasing the accuracy.
SWV method was applied to numerous drug active compounds. Because of thesensitivity and rapidity SWV is useful for drug analysis in their dosage forms and
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Table
2.SelectedexamplesofDPV
onpharm
aceuticalcompoundsin
theirdosageform
sandbiologicalmedia
Drugs
Electrodes
Medium
LOD=LOQ
Applications
References
Cefotaxim
eModified
graphite
pasteelectrode
H2SO
40.1mM
Human
blood
Nigam
etal.2009
L-ascorbic
acid
Acetaminophen
BDDE
pH
7.0
phosphate
buffer
0.01mM
Pharm
aceuticals
Radovan,Cofan,and
Cinghita2008
Pentoxifylline
GCE
pH
3.0
phosphate
buffer
4.42�10�10M
Pharm
aceuticals
Hedge
and
Nandibew
oor2008
Methim
azole
modified
CPEwitha
Schiffbase
complex
ofcobalt
pH
7.0
phosphate
buffer
5.0�10�7M
Pharm
aceuticalsand
clinicalpreparations
Shahrokhianand
Ghalkhan
i2008
Tetrazepam
Mercury
electrode
pH
7.0
BR
buffer
5.0�10�6M
Pharm
aceuticalshuman
serum
M.M.Ghoneim
etal.
2008
Pefloxacin
BDDE
0.5H
2SO
44.12�10�7M
Pharm
aceuticalshuman
serum
Usluet
al.2008
Bisoprololfumarate
SWCNTsmodified
GCE
pH
7.2
phosphate
buffer
8.27�10�7M
Pharm
aceuticalshuman
urine
Goyalet
al.2008
Repaglinide
CPE
GCE
pH
7.0
BR
buffer
1.35�10�7M
1.06�10�7M
Pharm
aceuticalshuman
serum
El-Ries,Mohamed,and
Attia
2008
Abacavir
HMDE
1M
H2SO
42.41�10�8M
Pharm
aceuticals
Doganet
al.2008
Cefdinir
Mercury
electrode
pH
2.0
phosphate
buffer
0.5�10�9M
Pharm
aceuticals
biologicalfluids
Jain,Radhapyari,and
Jadon2007b
Dopamine
Modified
GCE
pH
8.0
phosphate
buffer
0.2mM
–Mazloum-A
rdakoni
etal.2010
Etoposide
CPE
pH
3.0
BR
buffer
1.0�10�7M
Pharm
aceuticals
humanserum
A.E.Radi,
Abd-Elhany,and
Wahdan2007
Fluvastatinsodium
BDDE
pH
10.0
BR
buffer
1.37�10�7M
Pharm
aceuticals
humanserum
Doganet
al.2007
Atorvastatincalcium
BDDE
GCE
0.1M
H2SO
42.27�10�7M
2.11�10�7M
Pharm
aceuticals
humanserum,
humanurine
Dogan-Topal,Uslu,and
Ozkan2007
Piroxicam
MWCNTspaste
electrode
pH
6.0
acetate
buffer
0.1mg
mL�1
Pharm
aceuticals
Abbaspourand
Mirzajani2007
Glivec
GCE
pH
7.2
phosphate
buffer
3.3�10�8M
Pharm
aceuticals
Diculescu,Vivan,and
Brett
2006
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Pyrantelpamoate
DME
pH
4.6
BR
buffer
2.45�10�5M
Pharm
aceuticals
Jain
etal.2006
Sim
vastatin
GCE
0.1M
H2SO
42.71�10�7M
Pharm
aceuticals
biolgicalfluids
CoruhandOzkan2006
Sparfloxacin
GCE
––
Pharm
aceuticals
Kumar
etal.2006
Dopam
ine
Ascorbic
acid
modified
CPEwith
nanosizedcobalt
phthalocyanine
particles
pH
7.4
phosphate
buffer
3.0�10�6M
Drugsamples
G.T.Yanget
al.2006
Quetiapine
GCE
pH
3.5
acetate
buffer
4.0�10�8M
Pharm
aceuticals
humansserum,urine
Ozkanet
al.2006
Diospyrin
modified
GCEwith
cobalt
tetrasulfonated
phthalocyanine
pH
5.4
acetate
buffer
0.3nmol�
1Stem-bark
ofDiosyros
montanaRoxb
Costaet
al.2006
Atenolol
Gold
nanoparticles
modified
indium
tin
oxide
pH
7.2
phosphate
buffer
0.13mM
Pharm
aceuticalshuman
urine
Goyalet
al.2006
Valacyclovir
GCE
pH
10.0
BR
buffer
1.04�10�7M
Pharm
aceuticalshuman
serum,gastricfluid
Usluet
al.2006
Primaq
uine
GCE
pH
4.0
BR
buffer
4.2mg
mL�1
Pharm
aceuticals
Arguelho,Zanoni,and
Stradiotto2005
FlupenthixolHCl
GCE
pH
7.02BR
buffer
1.17�10�7M
Pharm
aceuticals
humanserum
Doganet
al.2005b
Vardenafil
GCE
pH
2.0
phosphate
buffer
2.3�10�8M
Pharm
aceuticals
humanserum
Uslu,Dogan,et
al.
2005a
Cefixim
eGCE
pH
4.5
acetate
buffer
6.4�10�7M
Pharm
aceuticals
urine,
breast
milk
Golcuet
al.2005
Paracetamol
Nanogold
modified
indium
tinoxide
pH
7.2
phosphate
buffer
1.8�10�7M
Pharm
aceuticals
Goyalet
al.2005
Bromocriptine
GCE
pH
5.0
BR
buffer
0.01mg
mL�1
Pharm
aceuticals
A.Radi,El-Shah
awi,
andElm
ogy2005
Sertindole
GCE
BDDE
pH
3.5
acetate
buffer
1.0�10�6M
Pharm
aceuticals
humanserum
Altunet
al.2009
Dopam
ine
Serotonine
m-indium
tinoxide
electrode
pH
7.2
phosphate
buffer
0.5Nm
3.0nM
Human
serum,urine
Goyal,Gupta,et
al.
2007
(Continued
)
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Table
2.Continued
Drugs
Electrodes
Medium
LOD=LOQ
Applications
References
Diazepam
Oxazepam
CPE
–0.021mg
mL�1
0.012mg
mL�1
Human
plasm
a,urine
Lozeno-C
haves
etal.
2006
Chloroquine
mCPE
pH
8.0
phosphate
buffer
3.0�10�8M
Human
serum
A.Radi2005
Lomefloxacin
Sparfloxacin
Gatifloxacin
CPE
–4.2�10�7M
7.0�10�7M
6.6�10�7M
Pharm
aceuticals
humanurine
Rieset
al.2005
p-A
minobenzoic
acid
CPE
pH
2.0
BR
buffer
0.1mg
cm�3
Pharm
aceuticals
KotkarandSrivastava
2006
Ganciclovir
GCE
pH
2.0
BR
buffer
8.1�10�8M
Pharm
aceuticals
humanserum
Uslu,DoganTopal,and
Ozkan2005b
Flupentixol
GCE
pH
7.02BR
buffer
1.2�10�7M
Pharm
aceuticals
biologicalfluis
Dogan,Ozkan,and
Uslu2005
Metronidazole
GCE
pH
9.0
BR
buffer
2.0�10�8M
Pharm
aceuticals
JiangandLin
2006
Mefloquine
GCE
pH
11.10BR
buffer
4.5�10�7M
Pharm
aceuticals
humanserum,urine
Uslu,Dogan,et
al.
2005b
Lam
ivudine
GCE
pH
4.5
acetate
buffer
6.3�10�8M
Pharm
aceuticals
humanserum
Dogan,Uslu,et
al.2005
Indinavir
GCE
pH
10.0
BR
buffer
1.3�10�7M
Pharm
aceuticals
humanserum
Doganet
al.2006
Salicyclic
acid
GCE
pH
7.0
phosphate
buffer
1.04mg
mL�1
Pharm
aceuticals
Torriero
etal.2006
Trimebutine
GCE
ACN-LiCl 4
0.3mg
mL�1
Pharm
aceuticals
Adhoum
andMonser
2005
Nim
esulide
GCE
0.05M
H2SO
45.0�10�8M
Pharm
aceuticals
biologicalfluids
Wanget
al.2006
Atenolol
GCE
pH
7.2
phosphate
buffer
0.16mM
Pharm
aceuticals
biologicalfluids
GoyalandSingh2006
Naproxen
BDDE
CH
3CN-LiClO
430nM
Pharm
aceuticals
Suryanarayanan
etal.
2005
Tryptophan
BDDE
pH
11.2
phosphate
buffer
1.0�10�6M
Realsamples
Zhao,Qi,andTian2006
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Estradiol
SPE
pH
7.2
phosphate
buffer
50pgmL�1
Human
serum
Pem
berton,Mottram,
andHart
2005
10-hydroxycamptothecin
CNT
0.5M
HClO
42.0�10�8M
Pharm
aceuticals
D.Sun,Wang,andWu
2006
Tryptophan
Tyrosine
GE
–1.0�10�5M
1.0�10�6M
Realsamples
Zhao,Qi,andTian2006
Nabumetone
GCE
pH
3.7
acetate
buffer
2.3�10�7M
Pharm
aceuticals
humanserum,urine
Altunet
al.2007
Verap
amil
GCE
pH
3.7
acetate
buffer
1.61�10�7M
Pharm
aceuticals
humanserum
Dem
ircanet
al.2007
Paracetamolcaffeine
BDDE
pH
4.5
acetate
buffer
4.9�10�7M
3.5�10�8M
Pharm
aceuticals
Lourencaoet
al.2009
Etofibrate
Fenofibrate
Atorvastatin
DME
–0.037–
0.21mg
mL�1
Pharm
aceuticals
humanplasm
a
Korany,Hew
ala,and
Abdel-H
ay2008
Opipramol
GCE
pH
3.5
acetate
buffer
2.7�10�7M
Pharm
aceuticals
humanserum,urine
TurhanandUslu2008
Donepezil
GCE
pH
7.0
BR
buffer
2.90�10�7M
Pharm
aceuticals
humanserum
GolcuandOzkan2006
Verap
amil
Graphite-polyurethane
composite
electrode
pH
5.3
acetate
buffer
0.7mm
olL
�1
Pharm
aceuticals
Sem
an,Cavalheiro,and
Brett
2009
Furosemide
Graphite-polyurethane
composite
electrode
pH
3.3.acetate
buffer
0.15mm
olL
�1
Pharm
aceuticals
Sem
anet
al.2008
Isoniazid
Modified
SPCE
pH
5.0
phosphate
buffer
1.7�10�7M
Human
urinesamples
Bergamini,Santos,and
Zanoni2010
Amlodipinebesylate
Atorvastatincalcium
GCE(ratio
voltam
metric
method)
pH
5.0
BR
buffer
8.01�10�7M
5.95�10�7M
Pharm
aceuticals
Dogan-Topal,Bozal,
etal.2009
Abbreviations:
SAM
AuElectrode:
scanningautomaticmicroscobeAuelectrode;
HMDE:Hangingmercury
dropelectrode;
SWV:Squarewavevoltam
metry;
DC:D
irectcurrent;DPV:Differentialpulsevoltammetry;NPV:Norm
alpulsevoltam
metry;LSV:Linearsw
eepvoltammetry;SMDE:Staticmercury
dropelectrode;
GCE:Glassycarbonelectrode;Modified
CPE:Modified
carbonpasteelectrode;ds-DNA
modified
PGE:Doublestranded
DNA
modified
pencilgraphideelectrode;
MWCNT-C
PE:multiwalled
carbonnanotubes
–carbonpasteelectrode;SWCNTmodified
CPE:singlewalled
carbonnanotubes
modified
carbonpasteelectrode.
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biological samples. The low detection and determination limits permit the analysis oftrace amount of drug compound. Various applications on pharmaceuticals andbiological samples are illustrated in Table 3.
Stripping Techniques
It is often necessary to employ some type of preconcentration step prior to theactual quantitation in the analysis of such dilute samples. This happens when the ana-lyte concentration is below the detection limit of the instrumental technique applied.Stripping voltammetric (SV) forms a subdivision of voltammetry and constitutes oneof the most important groups of electroanalytical techniques. SV is the best knownanalytical method that incorporates an electrolytic preconcentration step. The elec-troactive compound is deliberately accumulated from the solution phase onto a solidelectrode or into a liquid mercury electrode.
SV is composed of mainly four related techniques namely, anodic, cathodic,adsorptive voltammetric and potentiometric stripping. The compounds can be accu-mulated at the electrode by either faradaic (anodic, cathodic, potentiometric) ornon-faradaic (adsorption) process. Stripping methods involve a preconcentrationstep before analysis, either by forming an amalgam or complex with the particularanalyte and the electrode material or by adsorbing the substrate on the electrode sur-face (Kissinger and Heineman 1996; J. Wang 2006; Smyth and Vos 1992; Ozkan et al.2003; Bard and Faulkner 2001; Kellner et al. 2004; J. Wang et al. 1999; Brainina andNeyman 1993; J. Wang 1988; Harvey 2000; Gosser 1988; Koryta et al. 1993;Bagotsky 2006; Zoski 2007; Greef et al. 1990; Uslu and Ozkan 2007a, 2007b; Bond1980; Brett and Brett 1993; A. E. Radi 2006; Ozkan 2009).
The SV techniques involve three separate steps. Initially, electrochemicalaccumulation or the deposition step of the target electroactive compounds for theaccumulation into or onto the working electrode. During this step, at a depositionpotential, the solution is usually stirred. This step is provided during a preset timeat a given electrode potential and stirring of the solution or rotating electrode thatensures a steady flow of the analyte to the electrode surface. After the accumulationstep, the stirring process is stopped. The measurement (stripping) step follows thisstep, which involves the dissolution (stripping) of the deposited analyte.
Depending on the nature of the analyte, different modes of stripping analysisare used such as linear sweep, normal pulse, differential pulse, square wave, andpotentiometric methods (Kissinger and Heineman 1996; J. Wang 2006; Smyth andVos 1992; Harvey 2000; Gosser 1988; Koryta et al. 1993; Bagotsky 2006; Zoski2007; Greef et al. 1990; Bond 1980; Brett and Brett 1993; A. E. Radi 2006; Ozkan2009). Pulse voltammetric waveforms are especially useful for the stripping step asthey effectively correct for background current contributions. Using DPV andSWV modes as the stripping technique, the contribution of the current capacitycomponent to the registered current decreases, the detection limits (LOD) isimproved, and the possibility of a rapid determination of various elements and drugcompounds at a level 10�10M appears. However, the SWV technique has the addedadvantages of a faster scan rate and increased sensitivity compare with DPV.
The SV is an excellent technique for the determination of pharmaceuticalcompounds at trace levels (Kissinger and Heineman 1996; J. Wang 2006; Smyth
2664 B. USLU AND S. A. OZKAN
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Table
3.SelectedexamplesofdirectSWV
onpharm
aceuticalcompoundsin
theirdosageform
sandbiologicalmedia
Drugs
Electrodes
Medium
LOD=LOQ
Applications
References
Pefloxacin
BDDE
0.5M
H2SO
41.54�10�7M
Pharm
aceuticalsserum
Usluet
al.2008
Fluvastatinsodium
BDDE
pH
10.0
BRb
1.37�10�7M
Pharm
aceuticals
human
serum
Doganet
al.2007
Atorvastatincalcium
BDDE
GCE
0.1M
H2SO
42.27�10�7M
2.11�10�7M
Pharm
aceuticalshuman
serum,human
urine
Dogan-Topal
etal.2007
Sim
vastatin
GCE
0.1M
H2SO
42.71�10�7M
Pharm
aceuticals
biolgicalfluids
CoruhandOzkan2006
Quetiapine
GCE
pH
3.5
acetate
buffer
4.0�10�8M
Pharm
aceuticals
human
sserum,
human
urine
Ozkanet
al.2006
Valacyclovir
GCE
pH
10.0
BRb
1.04�10�7M
Pharm
aceuticalshuman
serum,gastricfluid
Usluet
al.2006
Primaquine
GCE
pH
4.0
BRb
4.2mg
mL�1
Pharm
aceuticals
Arguelhoet
al.2005
Flupenthixol
GCE
pH
7.02BRb
1.17�10�7M
Pharm
aceuticals
human
serum
Dogan,Ozkan,and
Uslu2005
Vardenafil
GCE
pH
2.0
phosphate
buffer
2.3�10�8M
Pharm
aceuticals
human
serum
Usluet
al.2005a
Cefixim
eGCE
pH
4.5
acetate
buffer
6.4�10�7M
Pharm
aceuticalsurine,
bristmilk
Golcuet
al.2005
Sertindole
GCE
BDDE
pH
3.5
acetate
buffer
1.0�10�6M
Pharm
aceuticalsserum
Altunet
al.2009
Mefloquine
GCE
pH
11.10BRb
4.5�10�7M
Pharm
aceuticals
serum,urine
Uslu,Dogan,et
al.
2005b
Lam
ivudine
GCE
pH
4.5
acetate
buffer
6.3�10�8M
Pharm
aceuticalsserum
Dogan,Uslu,et
al.2005
Nabumetone
GCE
pH
3.7acetate
buffer
2.31�10�7M
Pharm
aceuticals
serum,urine
Altunet
al.2007
Verap
amil
GCE
pH
3.7
acetate
buffer
1.33�10�7M
Pharm
aceuticalsserum
Dem
ircanet
al.2007
Etofibrate;
Fenofibrate
Atorvastatin
HMDE
–0.037–0.21mg
mL�1
Pharm
aceuticalsplasm
aKoranyet
al.2008
Opipramol
GCE
pH
3.5
acetate
buffer
2.7�10�7M
Pharm
aceuticals
serum,urine
TurhanandUslu2008
(Continued
)
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Table
3.Continued
Drugs
Electrodes
Medium
LOD=LOQ
Applications
References
Donepezil
GCE
pH
7.0
BRb
–Pharm
aceuticalsserum
GolcuandOzkan2006
Verapamil
Graphite-polyurethane
composite
electrode
pH
5.3
acetate
buffer
0.7mm
olL
�1
Pharm
aceuticals
Sem
anet
al.2009
Cefotaxim
eGCE
pH
2.0
BRb
2.8�10�7M
Pharm
aceuticalsserum
Dogan,Golcu,et
al.
2009
Amlodipinebesylate
Atorvastatincalcium
GCE(ratiovoltam-
metricmethod)
pH
5.0
BRb
8.53�10�7M
4.70�10�7M
Pharm
aceuticals
Dogan-Topal,Bozal,
etal.2009
Quinapril
HMDE
pH
10.0
BRb
0.22mg
mL�1
Pharm
aceuticals
SusluandAltınoz2008
Chlorpromazine
Propericiazine
Thioridazine
GCE
0.1M
HClO
4and
pH
2.0
phosphate
buffer
–Pharm
aceuticals
Mielech-Lukasiew
icz
etal.2008
Resveratrol
CPE
0.1M
HNO
3
(pH¼1)
5�10�9M
Pharm
aceuticalsurine
H.Zhanget
al.2007
Prednisone
Prednisolone
SWNT
EPPGE
pH
7.2
phosphate
buffer
0.45�10�8M
0.90�10�8M
Pharm
aceuticals
bodyfluids
GoyalandBishnoi2009
Acetylsalicylicacid
BDDE
0.01M
H2SO
42.0mM
Pharm
aceuticals
Sartoriet
al.2009
Adrenaline
Poly(1-m
ethylpyrrole)
mCPE
pH
4.0
phosphate
buffer
1.68�10�7M
Pharm
aceuticals
Aslanoglu
etal.2008
Lidocaine
BDDE
pH
2.0
BRb
10mg
mL�1
Pharm
aceuticals
Oliveira
etal.2007
Dopamine
Mercury
electrode
pH
7.5
citrate
buffer
0.02mg
mL�1
Pharm
aceuticals
Winter,Codognoto,and
Rath
2007
Ticlopidine
HMDE
pH
5.0
phosphate
buffer
5.17�10�7M
Pharm
aceuticals
TurkozandOnar2007
Fluoxetine
GCE
pH
9.0
borate
buffer
1.0mM
Pharm
aceuticals
Lencastre
etal.2006
Penicillamine
GCE
pH
5.0
acetate
buffer
0.08mM
Pharm
aceuticals
Shahrokhianand
Bozorgzadeh
2006
Pan
toprazole
HMDE
pH
5.0
BRb
0.048mg
mL�1
Pharm
aceuticalsplasm
aAltınozandSuslu2005
Captopril
SMDE
Sodium
sulfide
6.28�10�3mg
mL�1
Pharm
aceuticalsserum
Parham
andZargar
2005
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Trepibutone
PGE
pH
1.81BRb
20ngmL�1
Pharm
aceuticals
Gao,Song,
andWu
2005
Estradiol
Auelectrode
pH
7.4
phosphate
buffer
18pgmL�1
Biosensor
Liu,Duckworth,and
Wong2010
Captopril
mCPE
Aqueousbuffer
solution
9.1�10�8M
Urinesample
Karimi-Malehet
al.
2010
Levodopa
Dysprosium
nanowine
modified
CPE
pH
7.0
acetate
buffer
4.0�10�9M
Serum,urine
Daneshgar,Norouzi,
Ganjali,
Ordikhani-Seyedlar,
etal.2009
6-tioguanine
p-aminophenolmCPE
pH
9.0
universal
buffer
solution
0.08mM
Pharm
aceuticals
Mirmamtazet
al.2008
Mosapridecitrate
Ptelectrode
pH
6.0
phosphate
buffer
0.05mg
mL�1
Pharm
aceuticals
Jain,Radhap
yari,and
Jadon2008
Salbutamol
NGIT
OpH
7.4
phosphate
buffer
75ngmL�1
Pharm
aceuticalsplasm
a,
urine
Goyal,Oyama,and
Singh2007
Ketorolac
Tromethamine
Polypyrole
modified
CE
pH
5.5
acetate
buffer
1�10�12M
serum
Santhosh
etal.2007
Dipyridamole
HMDE
pH
3.0
phosphate
buffer
1.88�10�8M
Pharm
aceuticals
deToledo,Castilho,and
Mazo
2005
Cefoperazone
GCE
pH
2.00phosphate
buffer
1.31�10�7M
Pharm
aceuticalshuman
serum
Dogan,Golcu,et
al.
2009a
Nitrofurantoin
BDDE
pH
4.00BRb
8.15�10�9M
Pharm
aceuticals
deLim
a-N
etoet
al.2010
Dexamethasone
fullerene-C60-m
odified
edgeplanePGE
pH
7.2
phosphate
buffer
5.5�10�8M
Pharm
aceutical
form
ulations,human
bloodplasm
a
Goyal,Gupta,and
Chatterjee2009
Methyprednisolone
single-wallcarbon
nanotubes
modified
EPPGE
pH
7.2
phosphate
buffer
4.5�10�9M
Pharm
aceuticaldosages
andhumanblood
plasm
a
Goyal,Chatterjee,
and
Rana2009
Abbreviations:HMDE:Hangingmercury
dropelectrode;SWNT:Singlewallcarbonnanotube;EPPGE:Modified
edgeplanepyrolyticgraphiteelectrode;SMDE:
Staticmercury
dropelectrode;
PGE:Pencilgraphiteelectrode;
NGIT
O:Nano-gold
particlesmodified
indium
tinoxide;
SPCE:Screen-printedcarbonelectrode.
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and Vos 1992; Ozkan et al. 2003; Bard and Faulkner 2001; Kellner et al. 2004;J. Wang et al. 1999; Ozkan 2009). The major advantage of SV is its extremely lowdetection and determination limits (about 10�12–10�10M), which are the results ofa preconcentration step in which the analyte is accumulated onto or into the workingelectrode.
In pharmaceutical analysis, SV techniques are widely used and very popularbecause of low LOD and LOQ values, its accuracy and precision, as well as thelow cost of equipment compared to the other analytical methods.
Anodic Stripping Voltammetry (ASV)
In SV techniques, anodic stripping voltammetry (ASV) is a commonly andwidely used form. It involves the reduction of a compound or metal ion as the pre-concentration step. The preconcentration in ASV is based on electrolytic depositionand its subsequent dissolution from the electrode surface by means of an anodicpotential scan. The accumulated compounds are thus stripped out of the electrodein an order that is a function of each standard compound potential, and gives riseto anodic peak currents that are measured. The resulting peak current depends onvarious parameters of the deposition and stripping steps as well as on the character-istics of the metal ion (diffusion coefficient, number of electrons) and the electrodegeometry.
Some of the most practical electrodes for ASV are hanging mercury drop(HMDE), static mercury drop (SMDE), mercury film (MFE), carbon, iridium,platinum, gold and screen-printed electrodes (SPEs), and so forth. Newly introducedelectrodes in this area such as Bismuth film electrodes (BFEs) have also been used asan alternative to MFEs. The BFEs have low detection limits (e.g., 10�9M) and betterreproducibility results when compared with other solid electrodes.
This method has been widely used as the stripping analysis for determinationof metals in different samples such as in pharmaceutical dosage forms. The cathodicdeposition, at a controlled time and potential, is used for the preconcentration step.Generally, the deposition potential is about 0.4V more negative than standardelectrode potential (E0) for the least easily reduced metal ion to be determined.The target compounds or metal ions reach to the electrode surface by diffusion orconvention where they are reduced and concentrated as amalgams (for mercury elec-trode) or on the electrodes (solid electrodes). The solution stirring or electroderotation is performed to convection transport. This convection force is usually usedto facilitate the deposition step. The duration of the deposition step is selectedaccording to the concentration level and other requirements. The deposition timerequired is dependent on the sample concentration, between 1 and 10min periodsusually being sufficient for measurements in the range of 10�7M to 10�9M. Theobtained stripping voltammogram provides both qualitative identification (usingthe peak potential) and the quantitative information (from the peak height or area).This method has been the most widely used for stripping analysis in the determi-nation of metals. The preconcentration is done by cathodic deposition at a controlledpotential and time. In the ASV method, DPV and SWV modes are the most widelyused techniques for the stripping steps on drug and=or metal analysis in pharmaceu-tical dosage forms (Kissinger and Heineman 1996; J. Wang 2006; Smyth and Vos
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1992; Ozkan et al. 2003; Bard and Faulkner 2001; Kellner et al. 2004; J. Wang et al.1999; Brainina and Neyman 1993; J. Wang 1988; Harvey 2000; Gosser 1988; Korytaet al. 1993; Bagotsky 2006; Zoski 2007; Greef et al. 1990; Nicholson 1965; Kissingerand Heineman 1983).
The remarkable sensitivity, versatility, high accuracy, precision, and low costof ASV techniques has led to its application in a large number of analytical prob-lems. The ASV techniques are also widely used for trace metals in biological samplessuch as blood, serum, plasma, urine, and tissues. Actually, ASV is most frequentlyused for metals that form amalgams with mercury. This type of application is outof the aim of this review. The only pharmaceutically active compound applicationsand metal analysis in pharmaceutical dosage forms are listed in Table 4 with theirnecessary details.
Cathodic Stripping Voltammetry (CSV)
Cathodic stripping voltammetry (CSV) is another version of stripping voltam-metry and differs in the nature of the preconcentration and stripping steps. In CSV,an anodic preconcentration step is undertaken, which is followed by a potential scantoward more negative potentials, and reduction currents are measured. It is similarto the trace analysis method ASV, except the plating step where the potential is heldat an oxidizing potential, and the oxidized species are stripped from the electrodesurface by sweeping the potential positively. The CSV method involves anodic depo-sition of an insoluble film of material on the electrode; subsequently, it is stripped offduring a negative-going potential sweep. The CSV method is the mirror image of theASV method.
The HMDE is the most commonly used working electrode for CSV; although,silver, carbon-based, platinum, and other types of solid electrodes have been used inCSV techniques (Kissinger and Heineman 1996; J. Wang 2006; Smyth and Vos 1992;Ozkan et al. 2003; Bard and Faulkner 2001; Kellner et al. 2004; J. Wang et al. 1999;Brainina and Neyman 1993; J. Wang 1988; Harvey 2000; Gosser 1988; Zoski 2007).The CSV technique can be used to determine substances from insoluble salts withmercurous ion. Application of a relatively positive potential to a mercury electrodein a solution containing such substances results in the formation of an insoluble filmon the mercury electrode surface. The potential scan in the negative direction willthen strip (reduce) the deposited film into a solution. Solid electrodes such as silverand copper are less commonly used in CSV.
The preconcentration step improves selectivity, precision, and accuracy of themethod by isolating the analyte from the sample matrix, such as inactive ingredientsfrom pharmaceutical dosage forms and endogenous substances from biological sam-ples. Different voltammetric waveforms can be applied during the stripping step as inthe ASV techniques.
CSV is a widely utilized group of electroanalytical techniques for the determi-nation of trace analytes in pharmaceutical and clinical samples. Trace compoundanalyses in samples are challenging because of the low concentrations of the analytesat about between 10�9 and 10�12M. The CSV method is best suited for the determi-nation of a wide range of organic compounds especially sulfur compounds suchas penicillin, thiols, and inorganic anions, halides, sulfides, and so forth, that form
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Table
4.CSV
andASV
methodsforpharm
aceuticalcompoundsin
theirdosageform
sand=orbiologicalsamples
Compounds
Technique
Working
electrodes
Stripping
method
LOD
and=orLOQ
Applicationmedia
References
Sertraline
CSV
SMDE
SWV
1.5�10�7M
Pharm
aceuticals
Nouws,Delerue-Matos,
Barros,andRodrigu
es
2005
Rutin
CSV
HMDE
SWV
0.5nM
Pharm
aceuticals
EnsafiandHajian2006
Mn(II)
CSV
CPE
DPV
1.0�10�7M
Pharm
aceuticals
Rievajet
al.2008
Ascorbic
acid
CSV
HMDE
DPV
0.26ngmL�1
Pharm
aceuticals;human
serum
Prasadet
al.2009
Thiouracil
CSV
HMDE
DPV
2.0�10�11M
Pharm
aceuticals
Kasprzaket
al.2005
Metoclopramide
ASV
Modified
CPE
SWV
1.25ngmL�1
1.35ngmL�1
Pharm
aceuticals;human
urine
Farghaly
etal.2005
Methotrexate
(D-M
ethotrexate
and
L-M
ethotrexate)
ASV
CPE
SWV
6.79�10�10M
Pharm
aceuticals
El-Hadyet
al.2006
Sb(III)
ASV
Nanoparticle
modified
CSPE
DPV
9.44�10�10M
Pharm
aceuticals
RenedoandArcos
Martinez
2007
Sb(III)
ASV
Gold Nanoparticles
CSPE
DPV
0.2ngmL�1
Pharm
aceuticals
Renedoand
Arcos-Martinez
2007
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Riboflavin
ASV
Modified
CPE
SWV
6.5�10�7M
Pharm
aceuticals
Kotkaret
al.2007
Aurothiomalate
ASV
CSPE
LSV
3.0ngmL�1
Human
urine
BergaminiandZanoni
2006
Morphine
ASV
HMDE
DPV
0.1
ppb;0.2
ppb
Human
serum
Niazi
andYazdan
ipour
2008
Pb;Cd
ASV
HMDE
DPV
—Pharm
aceuticals
Modarres-Tehrani
etal.2007
Hg(II)
ASV
Gold Nanoparticle
modified
GCE
SWV
5.62ngmL�1
Pharm
aceuticals
Abollinoet
al.2008
Hydroxyzine
ASV
GCE
SWV
1.3�10�10M
Pharm
aceuticals;
Humanserum
Beltagi,Abdallah,and
Ghomeim
2008
Amoxicillin
ASV
Nafionmodified
GCE
DPV
1.27�10�8M
Pharm
aceuticals
Ramadan,Mandil,and
Saleh2008
Sb(II)
ASV
Mercury
Film
SPE
DPV
2.0�10�10M
Pharm
aceuticals
Dominguez-R
enedo
etal.2009
Amlodipine
ASV
CPE
SWV
2.0�10�11M
Pharm
aceuticals
Kazemipouret
al.2009
Abbreviations:CSV:Cathodicstrippingvoltam
metry;ASV:Anodicstrippingvoltam
metry;SMDE:Staticmercury
dropelectrode;HMDE:Hangingmercury
drop
electrode;
CSPE:Carbonscreen
printedelectrode;
SWV:Squarewavevoltam
metry;DPV:Differentialpulsevoltam
metry;GCE:Glassycarbonelectrode;
CPE:
Carbonpasteelectrode.
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insoluble salts with the electrode material. Table 4 lists the limited pharmaceuticaland biological applications that can be obtained using the CSV technique with theirrespective detection or determination limit and the stripping mode.
Adsorptive Stripping Voltammetry (AdSV)
The improvement of the quality of drug activity requires efficient research indrug design, safety, and bioavailability. Therefore, in order to achieve these targets,highly specific, sensitive, accurate, selective, and rapid analytical methods of phar-maceutically active compound analyses are necessary. Classical stripping voltamme-try such as ASV and CSV techniques are based on an electrolytic preconcentrationstep of the analyte from the solution onto the working electrode, generally HMDE.The principle of AdSV can be compared to the other stripping techniques such asASV or CSV except that no change is transferred during the preconcentration step.Accumulation of the analyte at the electrode surface is performed at an open circuitby applying a suitable potential at which no electrochemical reactions occur for settime. The main difference between other stripping voltammetric and AdSV techni-ques is the utilization of a spontaneous adsorption process during the preconcentra-tion step. After the equilibrium time, the potential is scanned by anodic or cathodicdirection depending on the redox properties of the investigated drug compounds.The adsorptive accumulation scheme results in very effective preconcentration,allowing highly sensitive measurements (about 10�11M levels) following shortadsorption times. To attain such high sensitivity, it is essential to optimize oper-ational variables such as nature of the supporting electrolyte, pH, accumulationpotential, and time that favor strong adsorption. In drug analysis, AdSV is remark-ably sensitive, selective, and, in particular, permits the determination of trace andultratrace concentrations of numerous pharmaceutical compounds.
The disadvantage of AdSV techniques is interference from other surface activesubstances in the sample solution. Interfering effects depend on the concentrationratio between analyzed and interfering substances and on their nature (Kissingerand Heineman 1996; J. Wang 2006; Smyth and Vos 1992; Ozkan et al. 2003; Bardand Faulkner 2001; Kellner et al. 2004; J. Wang et al. 1999; Brainina and Neyman1993; J. Wang 1988; Harvey 2000; Gosser 1988; Koryta et al. 1993; Bagotsky 2006;Zoski 2007; Greef et al. 1990; Nicholson 1965; Kissinger and Heineman 1983). Thistype of effect can be minimized and the sensitivity of AdSV techniques can be pre-served by employing a shorter accumulation time, applying the correct accumulationpotential, and using appropriate solution parameters such as pH, supporting electro-lyte, and ionic strength, among others.
The AdSV technique can be carried out at practically all types of electrodesemployed in voltammetry such as HMDE, SMDE, Pt, Ru, Au, glassy carbon, dia-mond, carbon paste, wax-impregnated graphite electrodes, and others. Most adsorp-tive procedures use HMDE or SMDE for measuring reducible species, which offersthe advantages of no need for surface cleaning, reproducible surface area, and elec-trochemical response and automatic control. The solid electrodes (Au, Pt, GC, CP,diamond, etc.) are especially suitable for studying adsorbable substances that can beoxidized at the electrode, because they can be polarized to more positive potentialthan a mercury electrode that, on the other hand, can be used in a wider negative
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potential range (Kissinger and Heineman 1996; J. Wang 2006; Smyth and Vos 1992;Ozkan et al. 2003; Bard and Faulkner 2001; Kellner et al. 2004; J. Wang et al. 1999;Brainina and Neyman 1993; J. Wang 1988; Harvey 2000; Gosser 1988; Koryta et al.1993; Bagotsky 2006; Zoski 2007; Greef et al. 1990; Kissinger and Heineman 1983;Rieger 1994; Sawyer, Sobkowiak, and Robert 1995). Thus, this is preferable forstudying both oxidizable and reducible substances.
The AdSV technique is a rapid and sensitive technique that has been success-fully applied for trace measurements of important pharmaceutical compounds dueto the high selectivity and sensitivity which it provides. Also, AdSV techniques havewide concentrations, about 10�11 to 10�3M, and require low-cost equipment com-pared to other analytical methods (Kissinger and Heineman 1996; J. Wang 2006;Smyth and Vos 1992; Ozkan et al. 2003). The AdSV techniques have been success-fully applied to the determination of many pharmaceutically active compounds invarious samples such as dosage forms, biological tissues, blood, urine, amongothrees. Short adsorption times between 1 and 5min show a very effective interfacialaccumulation. Table 5 lists the selected pharmaceutical active compounds that canbe determined using AdSV techniques together with ranges of their respectiveLOD and LOQ values.
Potentiometric Stripping Analysis (PSA)
Potentiometric Stripping Analysis (PSA) is another attractive version of strip-ping analysis, and it may provide a favorable alternative to voltammetric methodsfor determination of trace amount of metals and organic drug compounds. ThePSA technique was introduced by Jagner and Graneli in 1976 based on chemical oxi-dation of metals accumulated on mercury electrodes. Also, in 1991 Jin and Wangreported on a derivative adsorptive potentiometric stripping analysis where PSAwas extended to some organic compounds and metals that cannot be electrochemi-cally preconcentrated in mercury film. Extremely low detection limits at approxi-mately the mg �L�1 level are achieved due to the preconcentration step whencompared with normal potentiometric analysis. It comprises an initial preconcentra-tion step in which the analyte is accumulated onto or into the working electrode fol-lowed by a stripping step in which the analyte is stripped back into solution. It isbased on a two basic step approach: preconcentration and analysis. The depositionstep in PSA is the similar to the ASV techniques. Nonetheless, PSA signal is notdependent on the electrode surface, where the technique can use electrodes of any size,self-optimized stripping scan rate, analysis in solutions with lower ionic strength,lower background contributions, and so forth. The difference of the PSA techniquefrom the ASV technique is the re-oxidation of the amalgamated metals that are usedin PSA. In PSA, the metal is deposited as electrolytically onto the mostly mercury filmelectrode. The constant potential is applied to the working electrode for a fixed timeduring which target metal ions in analyte solution are reduced to their elemental stateand amalgamate with and are concentrated at the mercury electrode (Kissinger andHeineman 1996; J. Wang 2006; Smyth and Vos 1992; Ozkan et al. 2003; Bard andFaulkner 2001; Kellner et al. 2004; J. Wang et al. 1999; Brainina and Neyman1993; Harvey 2000; Bagotsky 2006; Zoski 2007). By far, the most common modeof preconcentration is the accumulation of substances or metal ions by the formation
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Table
5.Selectedexam
plesofadsorptiveandpotentiometricstrippingtechniques
onpharm
aceuticalcompoundsin
theirdosageform
sandbiologicalmedia
Compounds
Workingelectrodes
Techniques
Stripping
methods
LOD
and=orLOQ
Applicationmedia
References
Ethamsylate
SAM
AuElectrode
AdSV
SWV
6.0�10�8M
Pharm
aceuticals
X.H.ZhangandWang
2005
TriprolidineHCl
HMDE
AdSV
DC;DPV;SWV;
NPV
2.64ngmL�1
6.24ngmL�1
8.80ngmL�1
2.12ngmL�1
Pharm
aceuticals
Zayed
andHabib
2005
Tobramycin
HMDE
AdSV
LSV
3.44�10�9M
Pharm
aceuticals;human
urine;
serum
D.Sunet
al.2005
Trimethoprim
HMDE
AdSV
SWV
3.0ngmL�1
Pharm
aceuticals
Carapuca
etal.2005
Fluvoxamine
HMDE
AdSV
SWV
4.7�10�9M
Pharm
aceuticals
Nouws,Delerue-Matos,
Barros,Rodrigu
es,
Santos-Silvia
2005
Thalidomide
SMDE
AdSV
DPV;SWV
4.7
pg
0.5
pg
Pharm
aceuticals;human
urine;
serum
Cardoso
etal.2005
Norfloxacin;
Enoxacine
HMDE
AdSV
DPV
10mg
�mL�1
50mg
�mL�1
Pharm
aceuticals
Solangi,Khuhawar,and
Bhanger
2005
Cyclofenil
HMDE
AdSV
SWV
1.5�10�8M
Pharm
aceuticals;human
urine
Pacheco,Farias,and
Aucelio2005
Lamotrigine
HMDE
AdSV
DPV;SWV
4.68�10�9M;
5.02�10�9M
Pharm
aceuticals;human
plasm
a
Calvo,Renedo,and
Martınez
2005
Zafirlukast
HMDE
AdSV
SWV
5.0ngmL�1
Pharm
aceuticals
SusluandAltinoz2005
Carvedilol
GCE
AdSV
DPV;SWV
2.06�10�9M;
2.37�10�9M
Pharm
aceuticals;human
serum
DoganandOzkan2005
Selenium
CGDME
AdSV
LSV
50pgmL�1
Pharm
aceuticals
Kowalczyk,Lozak,and
Fijalek2005
Pefloxacin
DNA
Modified
electrode
AdSV
SWV
5.0�10�8M
Human
urine
A.Radi,ElRies,and
Kandil2005
Gatifloxacin
HMDE
AdSV
SWV
1.5�10�9M
Pharm
aceuticals;human
serum
El-Desoky2009
Chloroquine
Modified-C
PE
AdSV
DPV
3.0�10�8M
Human
serum
A.Radi2005
Cephalosporine
Antibiotics
HMDE
AdSV
SWV
7.0�10�10M
Raw
material
El-Maaliet
al.2005
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Daunomycin
Bismuth
AdSV
LSV
5nM
Raw
material
Buckova,Grundler,and
Flechsig2005
Ambroxol
HMDE
AdSV
DPV;SWV
0.2mg
mL�1
Pharm
aceuticals
Habib
andZayed
2005
Imatinib
HMDE
AdSV
SWV
5.19�10�8M
Human
urine
Rodrigu
ezet
al.2005
Lem
ofloxacin;
Sparfloxacin;
Gatifloxacin
CPE
AdSV
DPV
4.2�10�7M;
7.0�10�7M;
6.6�10�7M
Pharm
aceuticals
El-Reiset
al.2005
Griseofulvin
HMDE
AdSV
SWV
5.8�10�10M
Human
urine;
serum
El-Desoky2005
Pravastatin
HMDE
AdSV
SWV
8.0�10�8M
Pharm
aceuticals
Nigovicoc2006
Sb(III)
Sb(V
)
HMDE
AdSV
DPV
9.98�10�9M;
4.87�10�8M
Pharm
aceuticals
Gonzalez,
Dominguez
Renedo,andArcos
Martinez
2006
Citalopram
HMDE
AdSV
SWV
5.0�10�8M
Pharm
aceuticals
Nouws,Delerue-Matos,
andBarros2006
Danazol
HMDE
AdSV
SWV
5.7�10�9M
Pharm
aceuticals
Alghamdiet
al.2006
Nitroxynil
HMDE
AdSV
DPV
SWV
1.31�10�8M
8.4�10�10M
Pharm
aceuticals
M.M.Ghoneim
etal.
2006
Captopril
Pt
AdSV
LSV
9.2�10�7M
Pharm
aceuticals
Ziyatdinova,Budnikov,
andPogoreltsev2006
Paroxetine
HMDE
AdSV
SWV
4.8�10�7M
Pharm
aceuticals
Nouws,Delerue-Matos,
Barros,andRodrigu
es
2006
Diosm
inGCE
AdSV
LSV
3.5�10�8M
Pharm
aceuticals
El-Shah
awiet
al.2006
Thioguanine
DNA-m
odified
Au
electrode
AdSV
DPV
6.0�10�9M
Raw
material
S.F.Wanget
al.2006
Cefoperazone
HMDE
AdSV
SWV
4.5�10�10M
Human
urine;
serum
Hammam
etal.2006
Sulfadiazine
Sulfamethoxa
zole
HMDE
AdSV
DPV
0.002mg
mL�1
0.003mg
mL�1
Human
plasm
a;urine
Sabry
2007
Sb(III)
Sb(V
)
HMDE
AdSV
DPV
1.03�10�10M;
9.48�10�9M
Pharm
aceuticals;water
samples
Gomez
Gonzalezet
al.
2007
Oxcarbazepine
HMDE
AdSV
SWV
1.74�10�7M
Pharm
aceuticals
Calvoet
al.2007
Meloxicam
GCE
AdSV
LSV
0.02mg
mL�1
Pharm
aceuticals;human
urine;
plasm
a
Farhad
iandKarimpour
2007
(Continued
)
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Table
5.Continued
Compounds
Workingelectrodes
Techniques
Stripping
methods
LOD
and=orLOQ
Applicationmedia
References
Fluoxetine
HMDE
AdSV
SWV
2.2�10�7M
Pharm
aceuticals;human
serum;drug
dissolutionstudies
Nouwset
al.2007
Fluvoxate
HCl
HMDE
AdSV
SWV
LSV
1.0�10�9M
1.0�10�8M
Raw
material;
Pharm
aceuticals
M.M.Ghoneim,
El-Attar,andRazeq
2007
Terbutaline
GCE
AdSV
SWV
6.0�10�9M
Pharm
aceuticals;human
serum
Beltagi,El-Desoky,and
Ghoneim
2007
Piroxicam
HMDE
AdSV
SWV
0.143ngmL�1
Pharm
aceuticals;human
serum
Beltagi,Abdallah,and
Ghoneim
2007
Lem
ofloxacin;
Sparfloxacin;
Gatifloxacin;
Moxifloxacin
HMDE
AdSV
DPV
2.0�10�8M
Pharm
aceuticals;
biologicalsamples
Abdel
Ghani,El-Ries,
andEl-Shall2007
Folicacid
Leadfilm
electrode
onGCE
AdSV
SWV
7.0�10�10M
Pharm
aceuticals
Korolczukand
Tyszczuk2007a
Tolm
etin
HMDE
AdSV
SWV
2.0�10�9M
Pharm
aceuticals;human
serum
Beltagi,El-Attar,and
Ghoneim
2007
Dantrolene
HMDE
AdSV
LSV;SWV;DPV
1.8�10�9M;
2.1�10�10M;
3.0�10�9M
Raw
material;
Pharm
aceuticals
Ghoneim
etal.2007
Oxybutynin
chloride
HMDE
AdSV
DPV;SWV
0.23mg
mL�1
0.10mg
mL�1
Raw
material;
Pharm
aceuticals
Jain,Radhap
yari,and
Jadon2007a
Lamotrigine
ScreenPrinted
CarbonElectrode
AdSV
DPV
3.72�10�7M
Pharm
aceuticals
Calvoet
al.2007
Trimethoprim
Leadfilm
electrode
onGCE
AdSV
SWV
3.5�10�9M
Pharm
aceuticals;human
urine
Korolczukand
Tyszczuk2007b
Ketorolac
Modified
GCE
AdSV
SWV
1.0�10�12M
Human
serum
Santhosh
etal.2007
Clozapine
Modified
GCE
AdSV
DPV
5.0�10�9M
Human
serum
Farhadi,Yamchi,and
Sabzi
2007
Spiranolactone
HMDE
AdSV
SWV
3.5�10�9M
Pharm
aceuticals;human
urine;
serum
A.H.Al-Ghamdiet
al.
2008A.H.
Al-Ghamdiet
al.2008
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Testosterone
Leadfilm
electrode
onGCE
AdSV
SWV
9.0�10�9M
Pharm
aceuticals;human
urine
Tyszczuk2008
Lam
otrigine
Screenprinted
carbonelectrode;
Hgmodified
Screenprinted
carbonelectrode
AdSV
DPV
5�10�6M;
2�10�6M
Pharm
aceuticals
Dominguez-R
enedo,
Calvo,and
Arcos-Martinez
2008
Astem
izole
HMDE
AdSV
SWV
1.4�10�8M
Pharm
aceuticals;
biologicalfluids
Alghamdi2008
4-hexylresorcinol
MWCNTmodified
basalplane
pyrolyticgraphite
electrode
AdSV
CV
2mM
Pharm
aceuticals
Kachoosangi,
Wildgo
ose,and
Compton2008
Rutin
Single-sided
heated
graphite
cylindirical
electrode
AdSV
SWV
1.0�10�9M
Pharm
aceuticals
Wuet
al.2008
Fluvastatin
HMDE
AdSV
SWV
2.4�10�7M
Pharm
aceuticals
Neves,Nouws,and
Delerue-Matos2008
Imipenem
HMDE
AdSV
DPV
5.4�10�9M
Pharm
aceuticals;human
urine
Fernandez-Torres
etal.
2008
Vincamine
Nujol-basedCPE
AdSV
SWV
6.0�10�9M
Pharm
aceuticals;human
serum
Beltagi2008
Clarithromycin
HMDE
AdSV
LSV
SWV
22.41ngmL�1
11.2ngmL�1
Pharm
aceuticals;human
urine
M.M.Ghoneim
and
El-Attar2008
DL-a-tocopherol
DNA
modified
CPE
AdSV
SWV
0.056mg
mL�1
Pharm
aceuticals;foods
Suw,2008
Hydroxyzine
GCE
AdSV
SWV
1.5�10�8M
Pharm
aceuticals;human
plasm
a
Beltagiet
al.2008
Tetrazepam
HMDE
AdSV
LSV;DPV;SWV
3.0�10�9M
3.0�10�7M
Pharm
aceuticals
M.M.Ghoneim
etal.
2008
Rifampicine
Leadfilm
electrode
AdSV
SWV
9.0�10�11M
Pharm
aceuticals
Tyszczukand
Korolczuk2009b
Ketotifen
AuUltra
micro
electrode
AdSV
SWV
0.7pgmL�1
Pharm
aceuticals;
biologicalsample
Daneshgar,Norouzi,
andGanjali2009
(Continued
)
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Table
5.Continued
Compounds
Workingelectrodes
Techniques
Stripping
methods
LOD
and=orLOQ
Applicationmedia
References
Acetaminophen
Acetylsalicylic
acid
Dipyrone
Nanopolypyrrole
modified
GCE
AdSV
DPV
45pgmL�1
25pgmL�1
70pgmL�1
Pharm
aceuticals;human
urine
Muralidharanet
al.2009
Rutin
Leadfilm
modidied
GCE
AdSV
SWV
2.5�10�10M
Pharm
aceuticals
Tyszczuk2009
Candesartan
cilexetil
HMDE
AdSV
SWV
1.0�10�2mg
mL�1
Pharm
aceuticals
Suslu,Ozaltın,and
Altınoz2009
Efavirenz
ds-DNA
modified
PGE;BarePGE
AdSV
DPV
0.599ppm;
0.042ppm
Pharm
aceuticals
Dogan-Topal,Uslu,and
Ozkan2009
Diflunisal
Modified
CPE
AdSV
SWV
0.75ng�m
L�1
Pharm
aceuticals;human
blood
Beltagi2009
Glipizide
In-situplatedlead
film
electrode
AdSV
SWV
2.5�10�10M
Pharm
aceuticals;human
urine
Tyszczukand
Korolczuk2009a
Nitrofurantoin
HMDE
AdSV
SWV
0.06ngmL�1
Raw
material
Jain,Dwivedi,and
Mishra
2009
Haloperidol
HMDE
AdSV
SWV
3.83�10�10M
Pharm
aceuticalshuman
biologicalfluids
El-Desokyand
Ghoneim
2005
Entacapone
HMDE
AdSV
SWV
0.13ngmL�1
Pharm
aceuticals
Jain
etal.2010
Ethinylestradiol
HMDE
AdSV
SWV
5.90�10�10M
Pharm
aceuticalshuman
serum
andplasm
a
E.M.Ghoneim,
El-Desoky,and
Ghoneim
2006
Famotidine
Acontrolled
growth
mercury
drop
electrode
AdSV
SWV
4.90�10�11M
Human
serum
andurine
Skrzypek
etal.2005
Metoclopramide
CPE
AdSV
SWV
2.00�10�11M
Pharm
aceuticalsand
humanurine
Farghaly
etal.2005
Ofloxacine
HMDE
AdSV
SWV
1.10
�10
�8molL
�1
Pharm
aceuticalshuman
urineandserum
samples
A.F.Al-Ghamdi2009
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Tianeptine
HMDE
AdSV
SWV
0.3mg
mL�1
Pharm
aceuticals
Gazy
etal.2006
Zopiclone
GCE
AdSV
SWV
1.70�10�7M
Pharm
aceuticalsspiked
humanurine
Yılmaz2009
Moxifloxacin
HMDE
AdSV
SWV
0.44ngmL�1
Pharm
aceuticalshuman
urine
Trindade,
daSilva,and
Ferreira2005
Sildenafil
Leadfilm
modified
glassycarbon
electrode
AdSV
SWV
9.00�10�10M
Pharm
aceuticals
Tyszczukand
Korolczuk2010
Dopam
ine
Carbonnanotube
pasteelectrode
AdSV
SWV
4.0mg
L�1
Pharm
aceuticals
Ly2006
Nalidixic
acid
HMDE
AdSV
SWV
9.48
�10
�9MolL
�1
Urinesamples
Cabanillaset
al.2007
Niclosamide
carbon
nanoparticle=
chitosanfilm
(CNP=CS)
modified
GCE
AdSV
SWV
7.7nM
Pharm
aceuticalshuman
serum
Ghalkhan
iand
Shahrokhian2010
Cefadroxil
HMDE
AdSV
SWV
2.00
�10
�9molL
�1
Pharm
aceuticals
Alghamdi,Alghamdi,
andAl-Omar2009
Enrofloxacin
HMDE
AdSV
SWV
0.33nmolL
�1
Pharm
aceuticalshuman
plasm
a
Ensaifi
etal.2009
Dexamethasone
HMDE
AdSV
SWV
3.10�10�9M
Pharm
aceuticalsspiked
humanurine,
bovine
urine,
protein-free
bovinemilk
E.M.Ghoneim,
El-Attar,and
Ghoneim
2009
Acetaminophen
Dipyrone
Acetylsalicylic
acid
sodium
montm
orillonite
(NaMM)modified
GCE
AdSV
SWV
0.02mgmL�1
0.04mgmL�1
0.02mgmL�1
Pharm
aceuticalshuman
urine
Muralidharanet
al.2008
Losartan
HMDE
AdSV
SWV
0.15mg
mL�1
Pharm
aceuticals
Habib
etal.2008
Sim
vastatin
mercury
electrode
AdSV
SWV
4.50
�10
�9MolL
�1
Pharm
aceuticalshuman
serum
Nigovic
etal.2008
Losartan
Triamterene
mercury
electrode
AdSV
SWV
9.7nmolL
�1
0.3nmolL
�1
Pharm
aceuticalshuman
urine
EnsafiandHajian2008
(Continued
)
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Table
5.Continued
Compounds
Workingelectrodes
Techniques
Stripping
methods
LOD
and=orLOQ
Applicationmedia
References
Riboflavin
Plain
Carbonpaste
electrode
Chem
icallyModified
electrodewith
cyclam
AdSV
SWV
1.9
ngcm
�3
0.2
ngcm
�3
Pharm
aceuticalsand
foodsamples
Kotkaret
al.2007
Triamcinolone
acetonide
HMDE
AdSV
SWV
3.0�10
�10molL
�1
Pharm
aceuticalsand
humanserum
Hammam
2007
Norethisterone
Mercury
electrode
AdSV
SWV
1.50�10�9M
Pharm
aceuticals
M.M.Ghoneim,
Abushoff,et
al.2007
Cefazolin
Mercury
electrode
AdSV
SWV
2.60�10�10M
Pharm
aceuticals
El-Desoky,
Ghoneim,
andGhoneim
2005
Lamotrigine
HMDE
AdSV
SWV
5.02�10�9
moldm
�3
Pharm
aceuticalsand
humanserum
BurgoaCalvo,
Domınguez
Renedo,
andArcosMartınez
2005
Methocarbamol
CPE
AdSV
SWV
3�10�9M
Pharm
aceuticalsand
humanblood
E.M.Ghoneim
and
El-Desoky2010
Sildenafilsitrate
GCE
AdSV
SWV
2�10�9M
Pharm
aceuticals
TyszcukandKorolczuk
2010
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Secnidazole
GCE
AdSV
SWV
4�10�6M
Pharm
aceuticalsand
humanserum
El-Sayed
etal.2010
7,12 dim
ethylbenz
[a]anthracene
GCE=PGE
AdSV
DPV
0.194nM
Human
urinesample
Yardım
etal.2010
Pyridostigmine
bromide
HMDE
AdSV
SWV
andDPV
20.7ngmL�1
Pharm
aceuticalsand
biologicalfluids
Jain
etal.2010
Sertraline
Mercury
electrode
AdSV
SWV
1.50�10�7M
Pharm
aceuticals
Nouws,Delerue-Matos,
Barros,andRodrigu
es
2005
Ethamsylate
SAM
AuElectrode
AdSV
SWV
6.0�10�8M
Pharm
aceuticals
X.H.ZhangandWang
2005
5-Fluorouracil
MWCNT
PSA
–3.69ngL�1
Biologicalsamples
Chen
etal.2006
Anticancerdrugs
HeL
acellattached
Auelectrode
PSA
–Detection
Biologicalsamples
(cancercells)
El-Said
etal.2009
Sb(III);Sb(V
)MWCNT-C
PE
PSA
–6.2mg
L�1
Pharm
aceuticals
Santoset
al.2009
Zidovudine
HMDE
PSA
–0.25mM
Cellcultures
Vaceket
al.2004
Abbreviations:
HMDE:Hangingmercury
dropelectrode;
SMDE:Staticmercury
dropelectrode;
SAM
AuElectrode:
Self-assembledmonolayers
Auelectrode;
PGE:Pencilgraphiteelectrode;SWV:Square
wavevoltam
metry;DPV:Differentialpulsevoltam
metry;SMDE:Staticmercury
dropelectrode;CGDME:conrolled
growed
droppingmercury
electrode;
GCE:Glassycarbonelectrode;
CPE:Carbonpasteelectrode;
MWCNT-C
PE:multiwalled
carbonnanotubes–carbonpaste
electrode;
PSA:Potentiometricstrippinganalysis.
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of an amalgam in a mercury drop or thin film or solid electrode surface by electrolyticreduction at a fixed potential. The selection of the applied potential during thepreconcentration step is directly effected of the selectivity. The method allowsmulti-element detection and simultaneous determination in some pharmaceuticaldosage forms such as in vitamins. Amalgam forming elements such as copper, cad-mium, lead, zinc, can be determined simultaneously in this way. Approximatelytwenty amalgam-forming metals, including Cu, Zn, Cd, Pb, Sn, Bi, Tl, In, and Mn,are easily and simultaneously analyzed by PSA based on cathodic deposition ontomercury electrodes. Also, Se, Te, As, and Hg can be analyzed at bare solid electrodessimilar to gold and carbon electrodes (J. Wang 2006; Smyth and Vos 1992; Ozkanet al. 2003; Bard and Faulkner 2001; Kellner et al. 2004; J. Wang et al. 1999; Braininaand Neyman 1993; J. Wang 1988; Harvey 2000; Gosser 1988; Koryta et al. 1993;Bagotsky 2006; Zoski 2007). When monitored as a function of time, the potentialof the electrode provides an experimental curve analogous to a normal redox titrationcurve that contains the qualitative and quantitative information. After the depositionstep, the cell is left in an open circuit, and oxidation of the metal from the electrode isaffected by an oxidant diffusing to the electrode surface; the signal recorded is poten-tial as a function of time. It may provide a favorable alternative to voltammetricmethods for determination of trace amount of metals and some organic drug com-pounds. Modern PSA equipment uses microcomputers to register fast strippingevents and to convert the wave-shaped response to a more convenient peak over a flatbaseline. The limited examples of PSA applications on the determination of pharma-ceutically active compounds in their dosage forms and in biological samples are tabu-lated in Table 5.
Abrasive Stripping Analysis (AbSV)
Abrasive Stripping Analysis (AbSV) is a newly described stripping techniqueby Scholz et al. (Scholz and Lange 1992; Scholz et al. 1991; Scholz and Lange1990; Scholz et al. 1990; Scholz et al. 1989; Scholz, Schroder, and Gulaboski2005). The technique consists of the mechanical transfer of extremely small amountsof solid compounds by abrasion onto the surface of a suitable solid electrode. In thistechnique, the traces of solid particles are abrasively transferred onto the surface ofan electrode followed by an electrochemical dissolution that is recorded as a voltam-mogram. Usually, paraffin-impregnated graphite electrodes are used with this tech-nique. The abrased material is chemically stripped off. This process is traced withconventional electrochemical measuring techniques such as DPV, SWV, and LSV.After the measurement step of AbSV, the solid electrode surface is cleaned by rub-bing it onto a smooth filter paper. It allows the rapid and easy identification of solidmaterials and avoids the dissolution of the sample and, hence, reveals informationabout the structure of the solid material, thus allowing electrochemical phase analy-sis. This technique is easily applied to many fields of solid state analysis of theelectrochemistry of solid compounds. However, the application of AbSV on thepharmaceutical or biological analysis is very limited.
Komorsky-Lovric and Nigovic (2004) worked on the identification of5-aminosalicylic acid, ciprofloxacin, and azithromycin using the AbSV method.The CV and SWV techniques were used for their qualitative determination.
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The electrochemical characterization of simvastatin has been investigated atthe graphite and mercury electrode by Komorsky-Lovric et al. (2006). The graphiteelectrode reaction was found irreversible; the mercury electrode reaction was rapidand reversible.
Nigovic, Komorsky-Lovric, and Devcic. (2008) realized the identification ofsimvastatin using the AbSV method with the SWV technique at a paraffin-impregnated graphite electrode.
CONCLUSION
Electrochemistry is a well-established and rapidly growing area with a numberof possible applications in the pharmaceutical field. Modern electrochemical meth-ods are sensitive, selective, rapid, and provide easy techniques applicable to analysesin the pharmaceutical field and, indeed, in most areas of analytical chemistry. It isapparent that the electroanalytical techniques at varying levels of sensitivity arerequired to solve analytical-pharmaceutical problems. The advantages of electro-chemical methods are the ease of sample preparation and lack of interferences fromexcipients in the pharmaceutical dosage forms.
The improvement of quality of life has stimulated considerable research in drugdesign bioavailability and safety. Thus, to reach these targets, highly sensitive, spe-cific, and rapid methods of analysis are necessary. Thanks to the progress in electro-nics and computer sciences, from which electrochemical instrumentation has gainedconsiderable benefits in terms of precision, accuracy, sensitivity, and automation, theelectroanalysis of pharmaceutically active compounds is currently actively involvedin new research areas of stripping techniques. The main advantages of the strippingelectrochemical techniques are the higher sensitivity, wide concentration ranges,applicability of both reducible and=or oxidizable organic pharmaceutically activecompounds, and the low-cost equipment compared with the other analytical meth-ods. They are rapid techniques that have been successfully applied for trace measure-ments of important pharmaceutically active compounds due to the high sensitivityand selectivity that they provide. The aim of this review is to show that, for someanalytes and some types of matrices, especially drug dosage forms and endogenoussubstances, electroanalytical methods at all type of electrodes may be the bestmethod and can successfully compete with more widespread separation and spectro-metric methods.
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