Hydrocarbon selective
	Robust, linear, and stable
	Detects down to 1ppm levels
	Ceramic igniter runs hot to keep flame lit.

The FID detector is the most commonly used GC detector, responding linearly from its minimum detectable quantity of about 100 picograms to almost 100%. The FID response is very stable from day to day, and is not susceptible to contamination from dirty samples or column bleed. The FID detector responds to any molecule with a carbon-hydrogen bond, but not at all or poorly to compounds such as H2S, CCl4, or NH3. The carrier gas effluent from the GC column is mixed with hydrogen and then routed through an unbreakable stainless steel jet.

Unlike many other FID designs, the SRI FID detector employs a unique ceramic igniter which can run hot continuously, thus totally preventing the flame from extinguishing even when presented with large water injections or pressure surges from column backflush. The FID is thermostatted in an aluminum block up to 375°C and is equipped with a electrometer amplifier which has high, medium, and low gain settings. Hydrogen and air gas flows are controlled using Electronic Pressure Control ( EPC ) for high precision. The optional built-in "whisper quiet" air compressor ( part# SRI-8690-0070 ) is often used to supply the air for the FID, eliminating the bulky air cylinder.

Click here for printable FID technical overview (.pdf).
 

#SRI-8690-0010, FID DETECTOR

#SRI-8690-0070, BUILT-IN AIR COMPRESSOR 120VAC

#SRI-8690-2270, BUILT-IN AIR COMPRESSOR 220VAC

The SRI Methanizer consists of a 6" x 1/8" stainless steel tube which is mounted alongside the edge of the heated valve oven, and thermostatted to 380ºC. The tube is packed with a special nickel catalyst powder. Column effluent is mixed with 20 ml/min of hydrogen just prior to the methanizer entrance. Under these conditions, CO and CO2 are converted to methane while passing through the methanizer.

Hydrocarbons such as ethane, propane, etc. pass through the methanizer unaffected. Because the CO and CO2 are converted to methane, they can be detected by the FID down to 1 ppm, whereas the TCD can only detect CO or CO2 at 100 ppm at best. Detection limits are thus improved by a factor of 100. It is important to remember that the methanizer is located after the column ( and usually after the TCD detector ), so the CO and CO2 peaks pass through the column and TCD cell as CO or CO2. They are not converted to methane until they exit the column and TCD, so the retention times are not affected. The methanizer can not be mounted unless the GC is already configured with a valve oven. Methanizer tubes can be poisoned by large amounts of sulfur gas.

The SRI Methanizer accessory is available in three configurations:
1. Built into the FID detector.
2. Built into the valve oven ducts on the side of an 8610 GC (a valve oven must also be ordered).
3. As a stand alone unit for use with any FID detector.