Gas Chromatography – Flame Ionization Detector (GC-FID)

Gas chromatograph (GC)

is defined as a physical technique for the separation of volatile and semi-volatile compounds by passing a mobile carrier gas over a stationary phase. The Separation occurs as analytes partition in and out of the stationary phase while being carried through the column by the moving mobile phase. The major factor in separation is due to analytes having different affinities for the stationary phase.

A gas chromatograph consists of a carrier gas source, injection port, column, detector, and recording device. The injection port, column, and detector are temperature-controlled and may be varied as part of the analysis. The typical carrier gas is helium, nitrogen, or hydrogen, depending on the column and detector in use. The type of detector used depends on the nature of the compounds analyzed and Detector output is recorded as a function of time, and the instrument response, measured as peak area or peak height, is a function of the amount present.

Flame ionization detector (FID)

Considered as almost universal for organic compounds this is effectively the detector par excellence, of GC. The gas flow issuing from the column passes through the flame of a small burner fed by a mixture of hydrogen and air. The detector destroys the organic compound present whose combustion results in the release of ions and charged particles responsible for the passage of a very weak current between two electrodes (pd of 100 to 300 V).

GC-FID applications

• Volatile and semi-volatile organic substances, drugs & herbal extracts analysis
• Fatty acid composition analysis in Fats & oils
• OMEGA-3 fatty acids determination (Content of EPA and DHA)
• Organic Solvents purity testing
• Antiseptics contains Ethanol or isopropyl alcohol analysis
• Residual solvents analysis in raw materials and pharmaceutical dosage forms

References

• Francis Rouessac and Annick Rouessac textbook of chemical analysis Modern Instrumentation Methods and Techniques
• USP