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Flame Ionization DetectorMost common detector

Carbon atoms (C-C bonds) are burned in a hydrogen flame.

A small portion of carbon atoms are ionized (about in !"!!!)"

#he ions carry a charge from the flame to the $alls of the detector

$hich surrounds the flame.#he charge is electronically amplified

and sent to a recording de%ice.

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Flame Ionization Detector

%ery robust

and reliable.

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&itrogen 'hosphorus Detector

#he &'D uses a bead of a compound such as rubidium silicateabo%e a et of *. #he bead is heated by an electric current

forming a plasma. &itrogen and phosphorous react in the plasma

forming specific ions that carry a small current to the charged

collector. #he &'D is electronically similar to the FID" but sincethere is no flame" hydrocarbon ionization does not occur.

#he response to & is !+, ! greater than response to C

#he response to ' is !, ! .higher than response to C.

#he linear dynamic range is !

It is only fairly reliable since the bead burns up

o%er time causing drift in the signal.

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Flame 'hotometric Detector

#he (F'D) is an element specific detector

Commercial instruments are limited to the detection of ' and /

#he analytes are burned in a *flame causing electrons to

mo%e to an e0cited unstable state. 1hen the electrons return

to the ground state" they emit a specific $a%elength of light

*2 nm for ' and +3 nm for /

#hese $a%elengths are monitored by a photomultiplier" amplified"

and turned into an electrical signal.

#his detector is sensiti%e to !-3g

4inear dynamic range for ' of only !+, !.

For /" the response is non-linear.

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Flame 'hotometric Detector

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5lectron Capture Detector

#he 5CD uses a radioacti%e source such as &i2+$hich produces

6eta particles $hich react $ith the carrier gas producing free

electrons. #hese electrons flo$ to the anode producing an

electrical signal . 1hen electrophillic molecules are present"

they capture the free electrons" lo$ering the signal. #he amount

of lo$ering is proportional to the amount of analyte present.

It is sensiti%e do$n to !-but the dynamic range is only about !.

It7s an e0cellent detector for molecules containing an electronegati%e

group such as Cl or F etc. (or deri%itized molecules).

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5lectron Capture Detector

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Atomic 5mission Detector

8ne of the ne$est gas chromatography detectors9uite e0pensi%e compared to other :C detectors

#he strength of the A5D lies in the detector;s ability to

simultaneously determine elements. It uses micro$a%e energy

to e0cite helium molecules (carrier gas) $hich emit radiation

$hich brea

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Atomic 5mission Detector

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'hotoionization Detector

#he photoionization detector ('ID) uses a => lamp(0enon"

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'hotoionization Detector

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#hermal Conducti%ity Detector

Consists of an electrically-heated $ire or thermistor.

#he temperature of the sensing element depends on the thermalconducti%ity of the gas flo$ing around it. Changes in thermal

conducti%ity" such as $hen organic molecules displace some of

the carrier gas" cause a temperature rise in the element $hich is

sensed as a change in resistance.

#CD7s are often used to measure light$eight gasses or $ater(compounds for $hich the FID does not respond).

#he #CD is not as sensiti%e as other detectors but it is a

uni%ersal detector and is non-destructi%e.

Modern detectors called micro-#CD7s ha%e %ery small cell %olumes"

and ne$ electronics that produce much higher sensiti%ities and $ider

linear ranges. Due to its increased sensiti%ity" and the fact that it is a

uni%ersal non-destructi%e detector" it is again becoming more popular

for certain applications.

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#hermal Conducti%ity Detector

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#hermal Conducti%ity Detector

?epresentati%e #hermal Conducti%ity>alues" !! oC

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:C Detectors /ensiti%ities and ?anges