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Chromatogram

The chromatogram (see Figure 1) is the representation of the signal strength acquired by the detector vs. time. Before the analyte reaches the detector, we get some signal which is only noise and is called baseline. When the analyte reaches the detector, this signal starts increasing until a maximum and then decrease until all the analyte has been detected. This maximum corresponds to the peak height.

Graph with y-axis labeled detector response and x-axis labelled time. Sample injection baseline is a flat line just above zero. A red line curves upwards from the baseline at an example time point and peaks then curves downwards towards the baseline. There is an arrow from the baseline to the top of the peak labelled peak height. Another arrow from baseline to half the peak height is labelled height divided by 2. The retention time is the time from the injection point to the time of the peak height.

Figure 1. Example of a chromatogram.

The important parameters in chromatography are explained below. They are useful to interpret the chromatogram which is a representation of the processed signal strength vs. time.