What is a flame ionization detector?

A flame ionization detector (FID) is a detector that is paired with a gas chromatograph (GC) for the analysis of organic compounds.
An FID uses a flame, fuelled by hydrogen, to ionize the carbon atoms in organic compounds after they have been separated by the column in the GC.

Once the ions are formed they are collected and measured by the detectors electrodes. A current is produced as more charged ions are collected by the detector. The current is converted into an electrical signal which is displayed in either picoamperes (pA) or millivolts (mV).
Analytical results can be improved by using an inert make-up gas to provide additional gas flow to the ions as they travel through the detector.

What is flame ionization detection used for?

FIDs exhibit sensitivity and possess a wide dynamic range, rendering them well-suited for the detection of a diverse array of organic compounds. Widely employed in environmental analysis, the petrochemical industry, and other fields requiring precise identification and quantification of organic compounds, FIDs play a crucial role in analytical chemistry.

What does a flame ionization detection measure?

Flame ionization detectors measure ions per unit time which makes it a mass sensitive detector.

When should we use flame ionization detection?

Flame ionization detection is ideal for the measurement of hydrocarbons in the atmosphere. GC-FID analysis is useful for the analysis of organic compounds such as fatty acid methyl esters and total petroleum hydrocarbons. See our application library for a detailed look at GC-FID analysis.

What are the limitations of flame ionization detection?

The main limitation associated with flame ionization detectors is that they are only sensitive to organic compounds that can be burned in the flame. Inorganic compounds can not be detected by FID analysis. It is also possible that some organic compounds may not be able to be burned in the flame and therefore, will not be detected.

Another potential limitation of FID analysis is the lack of specificity – FIDs are unable to differentiate between different organic compounds so the use of individual reference standards is mandatory when two compounds co-elute.

What is the difference between flame ionization detection and mass spectrometry?

As stated above, flame ionization detection lacks in specificity and is unable to differentiate between two compounds that are not separated. Mass spectrometry (MS) is specific and is capable of determining between co-eluting compounds.

What are the advantages and disadvantages of flame ionization detection?

The main advantage of flame ionization detectors is that they are highly sensitive to organic compounds. They also have a fast response time – as combustion is almost instantaneous they are able to produce real-time measurements.

As well as being highly sensitive they are also highly selective for organic compounds. This is because the combustion of the samples is preferential to organic compounds containing (carbon and hydrogen) where as other compounds such as nitrogen will produce few to no ions.

As above, the main disadvantage of FID analysis is that it is unable to analyse inorganic compounds as well as lacking in specificity compared to other techniques such as mass spectrometry.