Solid Phase Microextraction(SPME)

What is an SPME?It consists of coated fibers that are used to isolate and concentrate analytes into a range of coating materials.

After extraction, the fibers are transferred to an analytical instrument for separation and quantification of the target analytes.

This is accomplished with the help of a syringe-like handling device that protects your sample while transferring from your sample to the instrument.

This syringe-like device also protects your fiber during storage. SPME, also known as Spee Mee, is a solvent-free adsorption/desorption technique.

More on SPMESPME is also a microextraction technique that, when compared to the sample volume, contains a very small amount of extraction solvent.

SPME allows for an equilibrium to be reached between the sample matrix and the extracting phase rather than an exhaustive removal of the analytes to the extracting phase occurring.The extracting phase is permanently attached to a rod that is made out of different materials, which makes this approach practical.

The amount of analyte adsorbed by the fiber depends on the thickness of the coating and on the distribution constant of the analyte.

Extraction time depends on the length of time required to obtain precise extractions for the analytes with the highest distribution constants.

Selectivity can be changed by altering the type of fiber used to match the characteristics of the analytes of interest.Volatile compounds require a thick coating and semivolatile analytes a thin coating.

How does SPME work?First, you draw the fiber into the needle.The needle is then passed through the septum that seals the vial.You then depress the plunger to expose the fiber to your sample or headspace above the sample.Organic analytes are then adsorbed to the coating on the fiber.After adsorption equilibrium is attained, which can be anywhere from 2 minutes to 1.5 hours, the fiber is drawn back into the needle and is withdrawn from the sample vial.Finally, the needle is introduced into the GC injector or SPME/HPLC interface, where adsorbed analytes are thermally desorbed and delivered to the instruments column.

Components of a Manual SPME HolderPlain HubThe O ringAdjustable needle guide/depth gaugePlungerPlunger retaining ScrewSPME manual holderSeptum piercing needleWhere fiber is exposed in headspace/liquid sample

SPME fibers availableFiber coating available:PDMSPDMS/DVBPolyacrylateCAR/PDMSCW/DVBCW/TPRStableFlex DVB/CAR/PDMSDifferent Phases available:Non-bondedstable w/ some water-miscible organic solventsslight swelling may occurNEVER use nonpolar organic solventsBondedstable with ALL organic solventsslight swelling possible w/ nonpolar solventsPartially Crosslinkedstable in most water-miscible organic solventsMay be stable in some nonpolar solvents, but slight swelling possibleHighly CrosslinkedEquivalent to the partially crosslinked, but some bonding to core has occurred in the past

StableFlex FibersThese type of fibers are coated on a flexible fused silica core instead of the standard fused silica core used on the other fibers.This coating partially bonds to the flexible core which results in: a more stable coating a more durable and longer lasting fiberThese special coated fibers are for GC use only .They also have the same temperature, conditioning, and cleaning requirements as the other fiber of its same coating and thickness.These are available in every coating EXCEPT for PDMS, Polyacrylate, and CW/TPR.

Polydimethylsiloxane (PDMS)

Film ThicknessDescriptionHubDescriptionRecommened use100mNon-bondedRed/plainVolatiles onGC/HPLC30mNon-bondedYellow/plainNonpolar semivolatiles onGC/HPLC7mBondedGreen/plainModerately polar to nonpolar semivolatiles onGC/HPLC

Polydimethylsiloxane/Divinylbenzene (PDMS/DVB)* This fiber is more durable due to it not containing any epoxy

Film ThicknessDescriptionHubDescriptionRecommened use65mPartially crosslinkedBlue/plainPolar volatiles onGC60m*Partially crosslinkedBrown/notchedGeneral purpose onHPLCStableFlex Fiber65mHighly crosslinkedPink/plainGC

Polyacrylate

Film ThicknessDescriptionHubDescriptionRecommened use85mPartially crosslinkedwhite/plainPolar semivolatiles onGC/HPLC

Carboxen/Polydimethylsiloxane (CAR/PDMS)

Film ThicknessDescriptionHubDescriptionRecommened use75mPartially CrosslinkedBlack/plainTrace-level volatiles onGCStableFlex Fiber85mHighly crosslinkedLt.Blue/plainGC

Carbowax/Divinylbenzene (CW/DVB)

Film ThicknessDescriptionHubDescriptionRecommened use65mPartially crosslinkedOrange/plainPolar analytes onGC

Carbowax/Templated Resin (CW/TPR)* This fiber is more durable due to it not containing any epoxy

Film ThicknessDescriptionHubDescriptionRecommened use50m*Partially crosslinkedPurple/plainSurfactants onHPLC

StableFlex Divinylbenzene/Carboxen/PDMS(DVB/CAR/PDMS)

Film ThicknessDescriptionHubDescriptionRecommened use50/30mHighly crosslinkedGray/plainGC50/30mHighly crosslinkedGray/notchedGC

Recommended Temperature and Conditioning for GC Use Maximum Operating Conditioning Time Phase Thickness Temperature Temperature Temperature (Hrs.)PDMS 100m 280C 200C-270C 250C 1 30m 280C 200C-270C 250C 1 7m 340C 220C-320C 320C 2-4PDMS/DVB 65m 270C 200C-270C 260C 0.5Polyacrylate 85m 320C 220C-310C 300C 2CAR/PDMS 75m 320C 240C-300C 280C 0.5CW/DVB 65m 265C 200C-260C 250C 0.5DVB/CAR/PDMS 50/30m 270C 230C-270C 270C 4

Note that the Polyacrylate, or white fiber, will turn brown as a result of condition and will not hurt the performance of the fiber.

Injecting and Running a Sample on GCThis is where you inject your SPME needle on the GC-MS

Advantages of SPMEDuring desorbtion of the analyte, the polymeric phase is cleaned and ready for reuse.

Absence of solvent makes SPMEenvironmentally friendly separation is fasterthroughput increases and allows for use of simpler instruments

Small in size great for field work. Amount of extracting phase is small and equilibrium of system is not disturbed Very small objects can be studied

High sensitivity and limit of determination

All extracted analytes are transferred to the analytical instrument

Can sample directly into a sample or the headspace above sample.

Range of analytes that can be analyzed include volatile, semivolatile, nonvolatile, and inorganic species.

coupled with other instruments besides GC like CE, LC, and MS.

When compared to similar extraction methods, SPME has a better detection limit, precision, cost, time, solvent use, and simplicity, which is shown in the table below.

Disadvantages of SPMECan get relatively expensive if one is not careful with fibers due to the cost being roughly $108 per fiber.

Polymer coating is fragile, easily broken, and have limited lifetime.

Also a monopoly with Supelco being the only suppliers of the fibers so cost continuously increases.

Its main limitation is its reduced concentration capability due to the small volume of polymer coating on the fiber, which is being addressed and researched further by Dr. Pawliszyn.

Comparing Extraction Methods for Pharmaceutical AnalysisSPE and LLE in drug analysis:Both complicated and time-consuming, which limits the number of samplesProne to sample loss due to being multi-stepRequire large sample amount Require an organic solventDifficult in automating these proceduresAdditional cost for waste treatment

SPME, as we have heard in previous slides, prevents all of these common drawbacks listed for SPE and LLE.

Why SPME?It can be used to analyze various types of analytes from gaseous, liquid, and solid samples instead of specializing in just one type like LLE or Headspace.

Very cheap compared to other extraction methods.

Reduces sample preparation times and disposal costs due to being solvent-free, also a bonus for the environment.

Improves detection limits.

A very simple methods that almost anyone could perform.

Conclusion SPME is a solvent-free microextraction technique that is:Cost efficientSimple to understand and useHigh sensitivityLow detection limitsCan be used to sample analytes of many typesUsed in many areas of industry

Referenceshttp://www.spme.uwaterloo.ca/SPMEdata/spmedata.html Pawliszyn, J. Solid Phase Microextraction : Theory and Practice. (1997) Publisher: (VCH, New York, N. Y.), 275 Arthur, C.L., Killam, L., Buchholz, K.D., Potter, D., Chai, M., Zhang, Z., Pawliszyn, J., Solid-Phase Microextraction: An Attractive Alternative, Environmental Lab. 11 (1992) 10-15 Z. Zhang and J. Pawliszyn, Headspace Solid Phase Microextraction. Anal. Chem. 65 (1993) 1843-852Z. Zhang, M. J. Yang and J. Pawliszyn, Solid Phase Microextraction: A New Solvent-Free Alternative for Sample Preparation, Anal. Chem. 66 (1994) 844A-853AR. Eisert and K. J. Levsen, Determination of Pesticides in Aqueous Samples by Solid-Phase Microextraction In-Line Coupled to Gas Chromatography-Mass Spectrometry, J. Am. Soc. Mass Spectrom. 6 (1995) 1119-1130 Z. Zhang and J. Pawliszyn, Sampling Volatile Organic Compounds Using a Modified Solid Phase Microextraction Device, J. High Res. Chromatogr. 19 (1996) 155-160Kataoka,H. Recent Advances in Solid-Phase Microextraction and Related Techniques for Pharmaceutical and Biomedical Analysis. Current Pharmaceutical Analysis. 1 (2005) 65-84Pragst, F. Application of solid-phase microextraction in analytical toxicology. Anal Bioanal Chem. 388 (2007) 1393-1414Vuckovic, D., E. Cudjoe, D. Hein, and J. Pawliszyn. Automation of Solid-Phase Microextraction in High-Throughput Format and Application to Drug Analysis. Anal. Chem. 80 (2008) 6870-6880Webster, G. R. Barrie; Sarna, Leonard P.; Graham, Kristina N. Solid phase microextraction. Tech. Aquat. Toxicol. (1996) 459-477