Chromatography is a powerful technique widely utilised in laboratories to separate and analyse complex mixtures.
A crucial element in this process is the detector, which supplies essential information about the mixture’s components. In this blog, we explore the various types of detectors used in gas and liquid chromatography, their functions, and maintenance tips.
A chromatography detector is a device used in gas chromatography (GC) or liquid chromatography (LC) to detect components of the mixture being eluted off the chromatography column.
The detector translates and provides information gathered by the chromatograph in a format usable to the technician. This information can then be stored and used by recording devices and computers, allowing technicians to analyse the data and make crucial decisions.
The important characteristics of chromatography detectors are as follows:
The Flame Ionization Detector (FID) is the most common detector used in gas chromatography.
It is sensitive to and capable of detecting compounds that contain carbon atoms (C), which accounts for almost all organic compounds. However, the FID is not sensitive to carbon atoms with a double bond to oxygen, such as in carbonyl groups and carboxyl groups (CO, CO2, HCHO, HCOOH, CS2, CCl4, etc).
The ultraviolet (UV) or visible detector is the most widely used in HPLC, providing good stability, ease of operation, and sensitivity for light-absorbing molecules up to the ~pg level. There are three types of detectors in UV/Vis:
After a Flame Ionization Detector, there are several other types of gas chromatography detectors commonly used, including:
Thermal Conductivity Detector
TCDs are universal detectors used in gas chromatography. They are popular for analysing gases and organic compounds and are often chosen when high sensitivity is not required.
Thermo Ionic Detector
Thermo ionic detectors are specialised detectors used to gauge and measure the presence of compounds featuring phosphorus or nitrogen atoms. They are not as widely used as FIDs and TCDs.
Flame Photometric Detector
These are used for detecting compounds with phosphorus or sulphur atoms in select applications.
Mass Spectrometry Detector (MS)
This detector ionises and fragments the isolated chemicals eluding from the column and calculates their mass-to-charge ratios, resulting in a mass spectrum that can be used to identify chemicals and determine their concentration.
High-Performance Liquid Chromatography (HPLC) also uses various detectors, each generating signals proportional to the sample mixture that emerges from the HPLC column.
We’ve already touched on ultraviolet detectors above. Here are some other common detectors used:
Fluorescence Detector
Fluorescence detectors irradiate the effluent with a light of a set wavelength and measure the fluorescence of the effluent at a single or multiple wavelengths.
Refractive index detector (RI or RID)
RIDs continuously measure the refractive index of the effluent. It’s the lowest sensitivity of all detectors and often used in size exclusion chromatography for polymer analysis.
Radio Flow Detector
Radio flow detectors measure the radioactivity of the effluent. This detector can be destructive if a scintillation cocktail is continuously added to the effluent.
Chiral Detector
Chiral detectors continuously measure the optical angle of rotation of the effluent. They’re used only when chiral compounds are being analysed.
Conductivity Monitor
A conductivity monitor continuously measures the conductivity of the effluent. They are utilised only when conductive eluents (water or alcohol) are used.
To ensure accurate results and extend the life of your chromatography equipment, regular maintenance and cleaning equipment thoroughly after each use is essential.
By doing this, you’ll be preventing unplanned downtime and ensuring results are as accurate for as long as possible. In turn, less time and stock will be wasted from failed experiments or equipment breakdowns.
We recommend servicing at least once per year, although frequent use may require more regular maintenance.
Choosing the correct detector for gas chromatography (GC) is essential for obtaining accurate and reliable analytical results.
When selecting a detector, consider:
By carefully evaluating these factors, you can select a detector that delivers efficient, and compliant results.
Understanding the different types of chromatography detectors and their maintenance is crucial for accurate and reliable results.
At LC Services, we are here to support your chromatography needs and our service contracts do vary and are dependent on you, your chromatography equipment, instruments, and the volume of business you have.
For more information about our servicing plans or advice on choosing the right equipment, please visit here: https://www.lcservicesltd.co.uk/service-contracts/
