How does a detector produce a chromatogram in gas chromatography?

In gas chromatography, a detector is placed at the exit of the column to sense separated components as they emerge from the mobile phase. The detector produces an electrical signal proportional to the amount or concentration of the solute present. This signal is then transmitted to a recording device, such as a computer or a strip-chart recorder, which plots the detector response as a function of time.123

The resulting graphic record is known as a chromatogram. On this plot, each separated component of the analyte appears as a distinct peak. The time elapsed between the initial injection and the detection of a component is called the retention time, which is used for qualitative identification. Quantitative analysis is performed by measuring the height or area of these peaks, which is proportional to the amount of the corresponding solute.24

Different types of detectors use various physical or chemical principles to generate these signals, such as measuring changes in thermal conductivity, detecting ions produced in a flame, or capturing electrons.1