What is a total ion current chromatogram?

Strictly speaking, it should be called a total ion current chromatogram; it is no longer a chromatogram, heh. The height on the vertical axis still represents the total ion signal generated by the substance, which is roughly proportional to the chromatographic peak area; of course, there are times when an ion current peak does not necessarily correspond to a chromatographic peak, and there are many special cases. A total ion current chromatogram consists of many peaks, which are arranged in the order in which they elute from the chromatograph. Within a single peak, there are also many fragments with different mass-to-charge ratios. In mass spectrometry, fragments with different mass-to-charge ratios within the same ion current peak are detected in ascending order, forming a mass spectrum. A point on the ion current chromatogram and a point on the mass spectrum are not necessarily pure, due to issues of chromatographic resolution and mass spectrometric resolution. Provided the column efficiency is sufficiently high and the analytical method is sufficiently robust, the substance at a given point on the total ion current chromatogram becomes increasingly pure; similarly, the higher the resolution, the higher the peak purity at a given point on the mass spectrum.