9 Types of Gas Chromatography Detector
Sep 02 2022
In chromatography, a detector is the device used to detect components being eluted off a chromatography column from a sample mixture. But not all detectors are equal. In this post, we’ll look at nine types of gas chromatography detector and their qualities.
Destructive gas chromatography detectors
The easiest way to categorise gas chromatography detectors is destructive and non-destructive. Quite simply, destructive detectors are those which transform the column effluent by burning or mixing, for example, making recovery harder or impossible. They include…
Flame ionization detector (FID)
A flame ionization detector works by heating the analyte using a hydrogen flame. A component within the analyte will then become ionized and lose an electron. That makes the flame more electrically conductive, triggering a measurable signal for the detector.
Flame photometric detector (FPD)
Similar to above, the flame photometric detector involves burning compounds in a flame. In this case, a photomultiplier tube is then used to detect spectral lines as specific elements emit light.
Nitrogen Phosphorus Detector (NPD)
A nitrogen phosphorus detector is specifically designed to selectively detect the two namesake elements based on the way they alter the function of metal bead.
Atomic-emission detector (AED)
With an atomic-emission detector, the sample enters a chamber after eluting from the column. It’s then energized to induce a plasma, which itself causes the sample to decompose. That creates an atomic-emission spectra from certain elements, which is then diffracted and detected.
Mass spectrometer (MS)
One of the most common detectors, a mass spectrometer is used to identify analytes based on their mass spectrum. It can also be used with liquid chromatography, as discussed in the article ‘Accelerating ADC Development with Mass Spectrometry’.
Non-destructive gas chromatography detectors
On the other hand, you have non-destructive detectors, which measure a property of the eluent directly, making recovery simpler and more effective. They include…
Thermal conductivity detector (TCD)
Also known as a katharometer, a thermal conductivity detector measures changes in thermal conductivity as a signal to detect compounds within an analyte.
Electron capture detector (ECD)
Electron capture detectors detect molecules in gas by attaching electrons to analyte molecules and measuring a change in current within a detector chamber – which is proportional to analyte concentration.
Photoionization detector (PID)
With a photoionization detector, gases are measured instantaneously. Typically used for volatile organic compounds, the detector uses UV rays to ionize molecules, causing them to release an electron and form a positive ion. That’s turned into a parts-per-million meter reading when electrodes collect those ions.
For this detection method, trained humans are used to smell gases and provide information about the presence of certain odours.
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