This document introduces the technical specifications of gas chromatograph detectors, including sensitivity, linearity, selectivity and repeatability. It also provides specific definitions and measurement methods for the relevant indicators, and finally summarizes the specific requirements for each indicator.
This document serves as a simplified guide to assist scientists in understanding detector specifications and relating them to specific analysis requirements. It addresses the lack of industry standards by providing a framework for evaluating vendor-provided data on sensitivity, linearity, selectivity, and repeatability.
The text focuses heavily on Detector Sensitivity, explaining why Minimum Detectable Level (MDL) or Signal-to-Noise (S/N) ratios are superior to simple response/mass values. It details the calculation of MDL for both mass flow detectors (e.g., FID) and concentration detectors (e.g., TCD), emphasizing the importance of specifying data rates and noise measurement conditions.
The S/N ratio assumed to represent the MDL should usually be given as 2.
Noise should typically be measured over a period of time that is about 10 times the peak width at half height.
A good method uses seven segments to measure the peak-to-peak noise after drift is removed, with contiguous segments having 10 percent overlap.