Introduction to Gas Chromatography for New and Advanced Users – Which GC detector do I really need?

What is a GC detector and what does it do?

Detectors in gas chromatography are used to determine the presence and quantity of the compounds injected and separated on dedicated GC column. The detector generally measures physicochemical property, and this data is converted into an electronic signal and plotted against retention time to obtain well known to us chromatogram.

The peak area and/or peak height found on chromatogram correspond to the amount of compound present in the sample injected, while the retention time can be used to distinguish the identity of the compound

GC detector types and why do I need a different detector(s)?

There are several gas chromatography detectors available, depending on the type of compounds and sensitivity you may require. Most people starting their GC adventure are essentially introduced to mostly FID detectors. Fortunately, depending on your analyses and targeted compounds you have more than one detector available. What is important is that you understand your sample, composition, matrix, which compounds you are targeting, do you need to see anything else than just compound of interest. All this will help you to select the right detector for the job ahead.

The ideal detector can be selected by simply:

• assessing the need for Universal or Selective detector – do I need to see everything or not
• assessing required sensitivity – am I looking for impurities or high conc. assay peaks
• ensuring good linearity – high linear range to cover you sample preparation concentration range
• being able to quantify and identify
• selecting non-destructive or destructive detector
• AND the most important detector must be fast, stable and easy-to-use

Potentially, all the above would ideally feature in one selected detector but as you probably guessed this is never the case. Therefore, in this part I will introduce you to some characteristics of commonly used GC detectors such as thermal conductivity detector (TCD), flame ionization detector (FID), electron capture detector (ECD), flame photometric detector (FPD), flame thermionic detector (FTD) and sulfur chemiluminescence detector (SCD) and barrier discharge ionization detector (BID). You might be surprised with all the new detector names, but it will is very easy to check which one is best suited for you, refer to table 1 below for an overview of each of detectors. On a closer view of the information in table 1, you will find that have other options to play with when it comes to GC system setup for your specific application/compounds.

Detectors are grouped into universal or selective/ specialized detectors. Universal detectors, like FID or TCD, detect all compounds with reference to carrier gas. On the other hand, detectors such as ECD are selective due to its operating principle where it only works for certain groups of compounds (e.g. halogens). These detectors, universal or selective, have their pros and cons. The use of universal detectors may cause you some headaches for complex samples with complicated matrices, while being too selective poses other challenges like omitting some compounds of interest. Therefore, the use of detectors must be specifically chosen and matched for your applications.

Table 1. Gas chromatography – most common detectors

Based on their principles, detectors can be classified into either concentration or mass detectors. Concentration detectors measure the concentration of compound present in the carrier gas flow. You must consider that this signal can be easily affected by the addition of make-up gases. On the other hand, mass detectors measure the total mass, or the compounds mass flow and the signal is independent of the amount of make-up gases.

Apart from these commonly used detectors, Shimadzu have also developed a new GC detector, a dielectric barrier discharge ionization detector (BID). It is a universal detector and comprises of a quartz tube, plasma generator and a separate charge collector. This technology enables the generation of atmospheric non-equilibrium helium plasma with low heat. The baseline noise is further reduced, and this allows the detections of trace components that are difficult to detect by other GC detectors. Also, the use of BID can replace the conventional multi-detection methods for the analysis of permanent gases and light hydrocarbons.

Refer to Figure 1 and Figure 2 below for a comparison of BID detectors with FID and TCD for analysis of alcohol mix and permanent gases, respectively.

Figure 1. Detectors comparison – BID and FID – alcohols mix and chlorine containing compounds

Figure 2. Detectors comparison – BID and TCD – mixture of gases

Are there any other detectors for GC?

There are, of course, other GC detectors that are not as widely known or used such as the atomic emission detectors; this lack in usage may be due to the limited suitability, unique applications and cost effectiveness of the detectors.

Sometimes it might not be possible to use universal detectors like TCD, or even very selective detectors such as ECD, especially in case of complex matrices analysis and multi-component complex samples. Known issues, such as coelution or lack of detection are well known, which makes data analysis and interpretation complicated. The routine detectors will only provide 2-dimensional data such as retention time and peak intensity/area. However, with the use of Mass Spectrometry (MS), it makes GC instruments more powerful, where the coupled instrument (GCMS) can differentiate co-eluting peaks, provide mass information and at the same time identify compounds with its library searching functionality. In GCMS, the compounds eluted are ionized and accelerated into the mass analyzer; mass analyzer separates all the ions based on their mass-to-charge (m/z) ratio and each intensity is recorded to give a mass spectrum. This intensity and m/z ratios can be used for both quantitative and qualitative purposes.

Refer to Figure 3 below for a graphical overview of GC detectors.

Figure 3. Different types of GC detectors

Summary

In summary, this blog covered the basics of GC detectors and introduced a variety of different GC detectors. Each of you can make their own judgement when selecting appropriate detectors for their next analysis. I can only ask you to consider other possibilities when running gas chromatography. Selective detectors can help you to “isolate” your analytes from a matrix and allow for much better sensitivity, on the other hand universal detectors will allow you to see more, should you need to look for other “unknown” species within your sample.

Gas Chromatography – Master the Basics

I hope that our third 2025 GC blog introduced you to gas carrier detectors employed in gas chromatography technique. It is never easy subject and becomes even more complex when considering carrier gas type and cost effectiveness of your analysis per sample.

Should you wish to discuss the GC technique and available GC instruments portfolio, please do not hesitate to contact me directly.