Flame Ionization Detector

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The Flame Ionization Detector responds to any molecu

The Flame Ionization Detector responds to any molecule with a carbon-hydrogen bond, but its responsele with a carbon-hydrogen bond, but its response is either poor or nonexistent to compounds such as H

is either poor or nonexistent to compounds such as H₂₂S, CClS, CCl₄₄, or NH, or NH₃₃. . Since the FID is masSince the FID is mass sensitive, nots sensitive, not concentration sensitive

concentration sensitive, changes in carrier gas flow rate have little , changes in carrier gas flow rate have little effect on the detector response. effect on the detector response. It is preferredIt is preferred for general hydrocarbon analysis

for general hydrocarbon analysis, with a detection range from 0.1ppm to , with a detection range from 0.1ppm to almost 100%. almost 100%. The FID’The FID’s responses response is stable from day to day

is stable from day to day, and is not susceptible to contamination from dirty samples or column ble, and is not susceptible to contamination from dirty samples or column ble ed. ed. It isIt is generally robust and easy to operate

generally robust and easy to operate, but because it uses a hydrogen diffusion flame to ioniz, but because it uses a hydrogen diffusion flame to ionize compounds for e compounds for analysis, it destroys the sample in the process.

analysis, it destroys the sample in the process.

Overview

The SRI FID features a

The SRI FID features a unique ceramicunique ceramic ignitor which can run hot contin

ignitor which can run hot continuously, and preventuously, and prevent the flame from extinguishing even with large water the flame from extinguishing even with large water injections or pressure surges from column injections or pressure surges from column backflush.

backflush. This ignitor This ignitor is positioned peris positioned perpendicular pendicular to the stainless steel detector jet and does not to the stainless steel detector jet and does not penetrate the flame.

penetrate the flame. Opposite this fOpposite this flame is thelame is the collector electrode.

collector electrode. This positively This positively charged metalcharged metal tube serves as a collector for the ions released as tube serves as a collector for the ions released as each sample component elutes from the

each sample component elutes from the column(s)column(s) and is pyrolyzed in the flame; it doubles as a vent and is pyrolyzed in the flame; it doubles as a vent for the FI

for the FID exhaust gas. D exhaust gas. The FID is The FID is equippedequipped with an electrometer amplifier which has HIGH, with an electrometer amplifier which has HIGH, HIGH (filtered), and

HIGH (filtered), and MEDIUM gain settings. MEDIUM gain settings. OnOn an SRI GC, the hydrogen and air gas flows are an SRI GC, the hydrogen and air gas flows are controlled using electronic pressure co

controlled using electronic pressure controllers,ntrollers, which are user adjustable via the GC’s front panel. which are user adjustable via the GC’s front panel. A thermostatted aluminum heater block maintains A thermostatted aluminum heater block maintains a stable detector temperature which is user a stable detector temperature which is user adjustable up to 375

adjustable up to 375oo_C._{C. The optional}_{The optional built-in ai}_{built-in air}_r

compressor may be used to supply the air for the compressor may be used to supply the air for the FID, eliminating bulky air cy

FID, eliminating bulky air cylinders. linders. The built-inThe built-in hydrogen generator is another option: the standard hydrogen generator is another option: the standard model can produce 20mL/min for use as both model can produce 20mL/min for use as both carrier gas and FID combustion gas at pressures carrier gas and FID combustion gas at pressures up to 25 psi. up to 25 psi. Collector Collector electrode electrode Ceramic Ceramic ignitor ignitor H H₂₂inin Air in Air in FID detector FID detector

(SRI Capillary FID GC with built-in Hydrogen Generator) (SRI Capillary FID GC with built-in Hydrogen Generator)

Detector viewport Detector viewport (remove Swagelok cap) (remove Swagelok cap) Thermostatted Thermostatted heater block heater block Flameport Flameport

Amplifier gain switch Amplifier gain switch Electrode lead Electrode lead to amplifier to amplifier

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FID - Flame Ionization Detector

In the SRI FID, the carrier gas effluent from the GC column is mixed with hydrogen,

In the SRI FID, the carrier gas effluent from the GC column is mixed with hydrogen, then routed throughthen routed through an unbreakab

an unbreakable stainless steel jet. le stainless steel jet. The hydrogen mix supports a diffusion flame at the The hydrogen mix supports a diffusion flame at the jet’s jet’s tip which ionizes thetip which ionizes the analyte molecules.

analyte molecules. Positive and negative ions are produPositive and negative ions are produced as each sample component is eluted into the flame.ced as each sample component is eluted into the flame. A collector electrode attracts the negative ions to

A collector electrode attracts the negative ions to the electrometer amplifierthe electrometer amplifier, producing an , producing an analog signal for theanalog signal for the data system input.

data system input. An electrostatic field is An electrostatic field is generated by the difference in generated by the difference in potential between the positivelypotential between the positively charged collector electrode and the grounded FID jet.

charged collector electrode and the grounded FID jet. Because of the electrostatic field, the Because of the electrostatic field, the negative ionsnegative ions have to flow in the direction of the collector electrode.

have to flow in the direction of the collector electrode.

Theory of Operation

The ratio of air to hydrogen in the combustion mixture should be approximat

The ratio of air to hydrogen in the combustion mixture should be approximately 10:1. ely 10:1. If the carrier flow isIf the carrier flow is higher than normal, the combustion ratio may need to be adjusted.

higher than normal, the combustion ratio may need to be adjusted. Flow is user Flow is user adjusted through the Electronadjusted through the Electronicic Pressure Controllers (EPC); the rates used to generate test chromatograms at the factory are printed on Pressure Controllers (EPC); the rates used to generate test chromatograms at the factory are printed on thethe right side of the GC in the flow rate chart.

right side of the GC in the flow rate chart. The FID temperature must be hot enough so that condensationThe FID temperature must be hot enough so that condensation doesn’t occur anywhere in the

doesn’t occur anywhere in the system; 150system; 150oo_{C is sufficient for volatile analytes; for semi-volatiles, use a higher}_{C is sufficient for volatile analytes; for semi-volatiles, use a higher}

temperature.

temperature. In addition to using In addition to using the ignitor to light the flame, it may be left on at an intermediate voltthe ignitor to light the flame, it may be left on at an intermediate voltage levelage level to prevent flameout (-750 or 7.5 volts)

to prevent flameout (-750 or 7.5 volts). . The ignitor is very durablThe ignitor is very durable and will last a long time, even at highe and will last a long time, even at high temperatures.

temperatures.

The FID hydrogen diffusion flame The FID hydrogen diffusion flame

FID detector schematic FID detector schematic

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Expected Performance

FID noise run FID noise run

Column: 15m MXT-1 Column: 15m MXT-1

Carrier: Helium @ 10mL/min Carrier: Helium @ 10mL/min FID gain = HIGH

FID gain = HIGH FID temp = 150 FID temp = 150oo_C_C FID ignitor = -400 FID ignitor = -400

T

Temperature pemperature program:rogram:

IInniittiiaall HHoolldd RRaammpp FFiinnaall 80

80oo_C_C ₁₁₅_5..0₀₀₀ ₀_0..0₀₀₀ ₈₈₀₀oo_C_C

Sample: 1mL of 1000ppm C Sample: 1mL of 1000ppm C₁₁-C-C₆₆ Carrier: Helium @ 10mL/min Carrier: Helium @ 10mL/min FID H

FID H₂₂at 25psi = 25mL/minat 25psi = 25mL/min FID air at 6psi =

FID air at 6psi = 250mL/min250mL/min FID temp = 150

FID temp = 150oo_C_C FID ignitor = -750 FID ignitor = -750 FID gain = HIGH FID gain = HIGH Valve temp = 90 Valve temp = 90oo_C_C

C C

1

1-C-C66 Hydrocarbon Test AnalysisHydrocarbon Test Analysis

Results: Results: C

Coommppoonneenntt ReRetteennttiioonn AArre ae a M Meetthhaanne e 00..88550 0 66997799..99226600 E Etthhaannee 22..886666 1133662233..77558800 P Prrooppaanne e 55..668833 1199553355..88996600 B Buuttaannee 88..220000 2266445566..55998800 P Peennttaannee 1100..228833 3333005533..99668800 H Heexxaannee 1122..991166 3399441199..00887700 Total 139069.2330 Total 139069.2330

FID noise averages less than 100µV from peak to peak FID noise averages less than 100µV from peak to peak

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Expected Performance

FID - Flame Ionization Detector

BTEX Test Analysis BTEX Test Analysis

15m MXT-VOL capillary 15m MXT-VOL capillary

column column FID gain = HIGH FID gain = HIGH FID temp = 150 FID temp = 150oo_C_C FID ignitor = -400 FID ignitor = -400 1µL 100ppm BTEX sample 1µL 100ppm BTEX sample Results: Results: C

Coommppoonneenntt ReRetteennttiioonn AArreeaa S Soollvveenntt 00..443333 9955887799..77556600 B Beennzzeennee 22..00883 3 883377..11000000 T TCCEE 22..77000 0 331199..22445500 T Toolluueennee 44..11883 3 11007700..11006600 P PCCEE 55..00000 0 334444..88664400 E Etthhyyl l BBeennzzeennee 66..22333 3 11220000..33332200 O Orrtthho o XXyylleennee 66..99000 0 11331122..33007700 B

Brroommooffoorrmm 77..11550 0 222255..22336600 tot

total al 101101188188.94.946060

The BTEX chemicals (Benzene, Toluene, Ethylbenzene, and Xylenes) are volatile monoaromatic The BTEX chemicals (Benzene, Toluene, Ethylbenzene, and Xylenes) are volatile monoaromatic hydrocarbons found in petroleum produ

hydrocarbons found in petroleum products like gasoline. cts like gasoline. Due to industrial spills and storDue to industrial spills and storage tank leakage, theyage tank leakage, they are common environmental pollutants.

are common environmental pollutants. Groundwater, wastewaterGroundwater, wastewater, and soil are , and soil are tested for BTEX chemicals intested for BTEX chemicals in many everyday situations.

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General Operating Procedure

2.

2. Set the FID Set the FID hydrogen flow to 25mL/min, hydrogen flow to 25mL/min, and the FID and the FID air supply flow air supply flow to 250mL/min. to 250mL/min. The approximateThe approximate pressures required are printed in the gas flow chart on the right-hand side of the GC.

pressures required are printed in the gas flow chart on the right-hand side of the GC. 3.

3. Ignite the FID by holding up the Ignite the FID by holding up the ignitor switch for a couple of seconds until you ignitor switch for a couple of seconds until you hear a small POPhear a small POP. . TheThe ignitor switch is locate

ignitor switch is located on the front panel of your SRI GC under the “DETEd on the front panel of your SRI GC under the “DETECTOR PCTOR PARAMETERS” heARAMETERS” headingading (it is labelled vertically: “FLAME IGNITE”).

(it is labelled vertically: “FLAME IGNITE”). 1.

1. Set the FID amplifier gain swiSet the FID amplifier gain switch to HIGH for most hydrocarbon applitch to HIGH for most hydrocarbon applications. cations. If peaks of interest go off theIf peaks of interest go off the scale (greater than 5000mV), set

scale (greater than 5000mV), set the gain to MEDIUM. the gain to MEDIUM. When peaks of interest When peaks of interest are 20 seconds wide or are 20 seconds wide or moremore at the base and extra noise immunity

at the base and extra noise immunity is desired, set the gain is desired, set the gain switch to HIGH (filtered). switch to HIGH (filtered). This setting broadensThis setting broadens the peaks

the peaks slightly.slightly.

5.

5. If you wish to keep the ignitor ON to prevent flameout, set the ignitor voltage to -750 by adjusting theIf you wish to keep the ignitor ON to prevent flameout, set the ignitor voltage to -750 by adjusting the trimpot on the “FLAME IGNITE” zone with the supplied screwdrive

trimpot on the “FLAME IGNITE” zone with the supplied screwdriverr.. 4.

4. VVerify that the FID flame is lit by holding theerify that the FID flame is lit by holding the shiny side of a chromed wrench directly in front of shiny side of a chromed wrench directly in front of the col

the collector lector outlet/FIoutlet/FID exhausD exhaust vent. t vent. If If condensation becomes visible on the wrench condensation becomes visible on the wrench surface, the flame is lit.

surface, the flame is lit.

FID amplifier gain switch FID amplifier gain switch

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Flame Ionization Detector - FID

FID Troubleshooting

Whenever you experience problems with your FID, review your operating

Whenever you experience problems with your FID, review your operating procedures: check the detector procedures: check the detector parameters, check to make

parameters, check to make sure you are on the sure you are on the correct channel of the data correct channel of the data system displaysystem display, check the , check the mixturemixture of hydrogen (25mL/min) and air (250mL/min)

of hydrogen (25mL/min) and air (250mL/min), check gas , check gas pressurpressures and connections, check the oven es and connections, check the oven andand detector temperatures, and all the other variables that

detector temperatures, and all the other variables that compose your analysis. compose your analysis. Having ruled out operatingHaving ruled out operating procedure as the source of the problem, ther

procedure as the source of the problem, there are two simple diagnostic tese are two simple diagnostic tests you can perform. ts you can perform. Detector Detector problems can be electrical or chemical in nature.

problems can be electrical or chemical in nature. Use the Flame ON/OFF tUse the Flame ON/OFF test to help determine if the problemest to help determine if the problem is of chemical origin.

is of chemical origin. Use the WUse the Wet Finger test to determine if the problem is electrical.et Finger test to determine if the problem is electrical. A.

A. Flame ON/OFF Flame ON/OFF TestTest 1.

1. Extinguish the flame by turning off Extinguish the flame by turning off the air.the air. 2.

2. Use the wrench test to make sure Use the wrench test to make sure the flame is OFFthe flame is OFF. . If it If it is, observe the baseline inis, observe the baseline in the chromatogram window to see whether there is an improvement or no change at all. the chromatogram window to see whether there is an improvement or no change at all. 3.

3. If baseline noise and high background disappear with the FID flIf baseline noise and high background disappear with the FID flame OFFame OFF, the, the problem is chemical in nature.

problem is chemical in nature. 4.

4. Isolate the column by capping off the column entrance to tIsolate the column by capping off the column entrance to the detector with ahe detector with a swagelok-type cap or a nut and septum.

swagelok-type cap or a nut and septum. Turn the air Turn the air back on and light the FID flback on and light the FID flame.ame. If the detector noise is similar to the background that was observed with the flame If the detector noise is similar to the background that was observed with the flame OFF

OFF, the column is susp, the column is suspect.ect. B. Wet Finger Test

B. Wet Finger Test

1. Make a V sign with the first two fingers of your right hand 1. Make a V sign with the first two fingers of your right hand.. 2.

2. Moisten those two fingers (Moisten those two fingers (you can achieve sufficient moisture by you can achieve sufficient moisture by licking them).licking them). 3.

3. Place one finger on the collector electrode, and place the other on bare metal (likePlace one finger on the collector electrode, and place the other on bare metal (like the FID detector body or the colum

the FID detector body or the column oven lid) to ground the collectorn oven lid) to ground the collector. . Make your Make your contact brief--you need only brush contact brief--you need only brush these parts to

these parts to perform the test. perform the test. BeBe careful not to burn yourself; the careful not to burn yourself; the column oven lid is probably cooler column oven lid is probably cooler than the FID dete

than the FID detector body.ctor body. 5.

5. Observing the milliVObserving the milliVolt reading on olt reading on the screen. the screen. If your If your contact makes a significan

contact makes a significant change in the milliVt change in the milliVolt reading,olt reading, then the FID

then the FID detector electronics are detector electronics are working. working. The dataThe data system signal should jump from zero to

system signal should jump from zero to the maximum voltagethe maximum voltage (5,000mV), then come back down when you remove (5,000mV), then come back down when you remove your your fingers.

fingers.

One finger here and One finger here and

the other finger here the other finger here

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The FID detector rarely requires

The FID detector rarely requires cleaning or servicing. cleaning or servicing. It may develop a film or coating of combustIt may develop a film or coating of combustionion desposits in the

desposits in the flameport with extended use. flameport with extended use. Use the FUse the FID detector viewport to ID detector viewport to check for visible check for visible deposits. deposits. If If you’re experiencin

you’re experiencing problems with your FID detector, try cleaning it, even if youg problems with your FID detector, try cleaning it, even if you can’t see deposits through the viewport.

can’t see deposits through the viewport. 1.

1. Unscrew the viewport cap nut and examine the flameport interior for Unscrew the viewport cap nut and examine the flameport interior for coatings or coatings or films.

films. If residue is If residue is found, the collector electrode and the flameport will need cleaning.found, the collector electrode and the flameport will need cleaning.

2.

2. Remove flameport assembly from Remove flameport assembly from the heater block the heater block a.

a. Disconnect the FID air supply line at the 1/16” bulkhead fitting.Disconnect the FID air supply line at the 1/16” bulkhead fitting.

b.

b. Using a philps head screwdriverUsing a philps head screwdriver, remove the screw on the top, remove the screw on the top of the FID’

of the FID’s heater block and pull s heater block and pull the aluminum cover up andthe aluminum cover up and off.

off.

c.

c. Gently pull off Gently pull off the white insulation tothe white insulation to reveal the detector

reveal the detector’s ’s bulkhead fitting onbulkhead fitting on the column oven wall.

the column oven wall. Loosen this fittiLoosen this fittingng to disconnect the flameport.

to disconnect the flameport.

3.

3. Remove the Remove the collector electrodecollector electrode a.

a. Unclip Unclip the the electrode electrode leadlead terminal and slide it off the terminal and slide it off the electrode.

electrode.

b.

b. Loosen and remove the nuLoosen and remove the nut and ferrule tt and ferrule that hold thehat hold the collector electrod

collector electrode in the flameport body.e in the flameport body.

c.

c. Slide the Slide the collector electrode out collector electrode out of the of the nut. nut. Once removed,Once removed, spin it between your fingers in a piece of san

spin it between your fingers in a piece of sandpaper to clean thedpaper to clean the stainless steel sur

stainless steel surface. face. A wire brush may alsA wire brush may also be used to scrubo be used to scrub the electrode.

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Cleaning the FID continued

4.

4. Remove the FID Remove the FID ignitor elementignitor element a.

a. The ignitor element is britThe ignitor element is brittle and will break when stresstle and will break when stressed, so handle theed, so handle the ignitor carefully

ignitor carefully, mindful of any torque on the blades. , mindful of any torque on the blades. While holding the ignitor While holding the ignitor by the ceramic body with one hand, loosen the 1/4” swagelok-type nut that by the ceramic body with one hand, loosen the 1/4” swagelok-type nut that

holds it in place.

holds it in place. There is a graphite ferrule inside this There is a graphite ferrule inside this nut that secures thenut that secures the ceramic ignitor body when the nut

ceramic ignitor body when the nut is tightened.is tightened. b.

b. Carefully pull Carefully pull the ignitor the ignitor down out of down out of the flameport. the flameport. Disconnect the ignitor Disconnect the ignitor from the spring-loaded ignitor current source termi

from the spring-loaded ignitor current source terminals. nals. Set the ignitor securelySet the ignitor securely aside.

aside.

5.

5. Use a wire brush or Use a wire brush or a sharp object to remove any residue from the flameport interior, then rinse it witha sharp object to remove any residue from the flameport interior, then rinse it with solvent (methanol or methylene chloride), and bake

solvent (methanol or methylene chloride), and bake it out in the GC’s column oven at 250it out in the GC’s column oven at 250oo_{C for 10-15}_{C for 10-15}

minutes. minutes.

6. Re-assembly 6. Re-assembly

a.

a. Once all the FID Once all the FID parts are cleaned, reverse the disassembly process, starting with the parts are cleaned, reverse the disassembly process, starting with the replacemenreplacementt of the ceramic ignitor

of the ceramic ignitor. . Leaving out the cleaning steps, your last step should be reinstalling Leaving out the cleaning steps, your last step should be reinstalling the flameportthe flameport assembly onto the heater block.

assembly onto the heater block. Make sure to position the ignitor so that the blade is slightly belowMake sure to position the ignitor so that the blade is slightly below and angled 10-15

and angled 10-15oo_{toward the jet’s tip so that the ignitor will not interfere with the flame or create}_{toward the jet’s tip so that the ignitor will not interfere with the flame or create}

turbulence. turbulence. Graphite ferrule Graphite ferrule Ignitor blade Ignitor blade Ignitor body Ignitor body

Scrape, rinse, and bake out the

Scrape, rinse, and bake out the FID flameport interior FID flameport interior

FID ignitor removed from FID ignitor removed from the flameport; note the the flameport; note the slight angle of the blade slight angle of the blade element element Ignitor blade Ignitor blade must not must not touch FID jet touch FID jet

Position the collector electrode Position the collector electrode so that about 1/8” of it is visible so that about 1/8” of it is visible through the viewport

through the viewport Use the viewport to correctly position the

Use the viewport to correctly position the FID ignitor FID ignitor and collector electrode inside the

and collector electrode inside the flameportflameport VIEW

VIEW

Flame Ionization Detector - FID

FID ignitor removed from the flameport assembly FID ignitor removed from the flameport assembly