GC-FID analysis

What is GC-FID analysis used for?

GC-FID is primarily used in industry and research to characterize mixtures of organic compounds. In pharmaceutical testing, the method can be used to identify residual contaminants, in polymer analysis to quantify residual monomers, and in the petrochemical industry to identify and quantify different hydrocarbon components in oil and other fuels.

GC-FID can also be used in food testing to determine the fatty acid profile of food. In environmental research, the technique can be employed to identify resin acids in water and contaminants in air samples.

How does GC-FID work?

Initially, the sample is passed through a gas chromatography column. This evaporates volatile compounds and causes the resultant gaseous mixture to be separated into individual components. Once the sample reaches the end of the column, it enters the flame-ionization chamber, where it is mixed with hydrogen and a suitable oxidant. This mixture is then burned with a hydrogen flame, causing any chemical components to become ionized and giving them a positive charge.

Above the flame is a negatively charged collector plate. As the positive ions emerge, they are accelerated towards the collector plate where, upon making contact, they induce an electric current. This current is measured, with the amount of current being related to the number of carbon atoms burned. By logging the data, it is possible to determine which components were present in the original sample, and in what quantities.

Sample requirements and preparation

GC-FID samples are generally prepared by dissolving or mixing the material in a low-boiling-point solvent, such as methanol. This solution is then injected into the chromatograph, which will cause it to vaporize rapidly into the gas phase. Note that solid organic samples can be analyzed this way, provided that they become volatile once dissolved.

GC-FID vs. GC-MS – What are the differences?

Gas chromatography–mass spectrometry (GC-MS) starts the same way as GC-FID, by separating the sample in the gas chromatograph. However, instead of a flame ionization detector, the sample is then passed through a mass spectrometer, which further separates and measures the ions based on their mass-to-charge ratio.

Typically, GC-MS is most useful when it comes to qualitative analysis, such as identifying unknown compounds and molecules based on their size. GC-FID, on the other hand, provides higher accuracy in quantifying many components.

To achieve a comprehensive set of results, GC-MS and GC-FID are often used in tandem with each other. A good example of this is NIAS testing of food contact materials, where the combined GC-MS/FID method can be used to first identify previously unknown components (with the MS detector) and then quantify them (with FID).

Need an analysis?

Measurlabs offers high-quality GC-FID measurements for different industries and fields of research. Many of these analyses have further details on prices and turnaround times available in our online catalog. Check out, for example, this purity assay of organic solvents, which combines GC-FID with Karl Fischer titration to determine solvent purity.

To get a customized quote, including any available volume discounts for large sample batches or recurring orders, please contact us through the form below. We will get back to you within one business day.