The Operation of the FID

The FID is probably the simplest, easiest and most reliable detectors to operate. Generally the appropriate flow rates for the different gases are given in the detector manual. Hydrogen flows usually range between 20 and 30 ml per min, air flows about 6 times the hydrogen flow e.g. 120 to 200 ml per min. The column flow that can be tolerated is usually about 20-25 ml per min depending on the chosen hydrogen flow. However, if a capillary column is used, the flow rate may be less than 1 ml per min for very small diameter columns. The mobile phase can be any inert gas–helium, nitrogen, argon etc. To some extent the detector is self-cleaning and rarely becomes fouled. However, this depends a little on the substances being analyzed.

Courtesy of Supelco Inc.

 

1/ Isobutane	2/ n-Butane	3/ Isopentane
4/ n-Pentane	5/ 2,3-Dimethylbutane	6/ 2-Methylpentane
7/ 3-Methylpentane	8/ n-Hexane	9/ 2,4-Dimethylpentane
10/ Benzene	11/ 2-Methylhexane	12/ 3-Methylhexane
13/2,2,4Trimethylpentane	14/ n-Heptane	15/ 2,5-Dimethylhexane
16/ 2,4-Dimethylhexane	17/2,3,4Trimethylpentane	18/ 2,3-Dimethylhexane
19/ 2,3-Dimethylhexane	20/ ethylbenzene	21/ m-Xylene
22/ p-Xylene	23/ o-Xylene	24/ -Me-3-Ethylbenzene
25/ 1,3,5-TriMe-benzene	26/ 1,2,4-TriMe-benzene	27/ 1,2,3-TriMe-benzene
28/ Naphthalene	29/ 2-Methylnaphthalene	30/ 1-Methylnaphthalene
31/ Dimethylnaphthalene

Figure 20. The Analysis of Gasoline