The flame ionization detector (FID) is very popular in the detection of organic compounds. Substances are pyrolysed in a hydrogen–oxygen flame and produce ions in the process. The carrier gases are nitrogen, helium, or hydrogen. Hydrogen is preferable for faster analysis, better separation of substances, and general usefulness with both packed- and capillary-column GC. The detection of FAs is quantifiable, and only formic acid is difficult to analyze due to low sensitivity. The usual sensitivity of the FID is to pictograms of FAME. Examples of FID detection of FAs in GC analysis are numerous [199–201]. Hartmann [202] has described the organophosphorus-sensitive flame ionization detector. The detector can be especially useful in the analysis of derivatives of FAs.