Gas Chromatography – Electron Capture Detector or GC-ECD is a technique used to analyse halogenated compounds and is primarily used in the environmental, forensic and pharmaceutical markets. Within an ECD, when certain molecules pass by the detector, they capture some of the electrons in the sample and this reduces the current measured. The compensation for this reduction is recorded as a positive peak.
As common with other GC techniques, a carrier gas is required with low Water and Oxygen impurities since Water and Oxygen can interact with the stationary phase and cause significant problems such as high baseline noise and column bleed in the output gas chromatogram which both reduces the analyser sensitivity and decreases column lifetime. Oxygen and Water impurities can also oxidise the radioactive Nickel source and reduce the detector response. In addition the carrier gas must have exceptionally low levels of Halocarbons as the ECD is extremely sensitive to these compounds.
The ECD also requires a make-up gas if Helium is used as the carrier gas since this serves to provide the electrons which are not contained within the Helium. The routine calibration of the analyser using a calibration mixture is common.
Our range of Experis® ultra high purity gases and patented BIP® technology offer you the optimum gas for your GC-ECD requirements. Don’t forget that your choice of cylinder equipment also affects your analytical results. Our range includes high quality cylinder regulators, manifolds, valves and purge systems which will help to optimise the smooth operation and accuracy of your analysis. For GC-ECD it is important to only use equipment that is approved for use with ECD.
The recommended gases and equipment for this application are listed below. Please note that our recommendation is based on common analytical requirements, so you may require a higher purity grade if analysing to lower concentrations or be able to use a lower purity grade if analysing to higher concentrations. If you require any additional advice on the right purity grade for your needs, please contact us.