What is Gas Chromatography?
A gas chromatograph is most often used to separate compounds found in extracts of environmental samples. A gas chromatograph is a temperature controlled oven that contains an internally coated capillary column typically 30 meters long with a 0.25 millimeter internal diameter onto which 1 or 2 L (1 or 2 millionths of a liter) of a sample extract is injected. Ideally, each compound is retained by the coating to a different extent as they travel the length of the column and each compound exits alone into the ion source of the mass spectrometer after a retention time specific to that compound. If one plots the ion abundance vs time for the compound’s molecular ion or other ions characteristic of the compound, a chromatographic peak is observed. The Total Ion Chromatogram is a plot of the sum of ion abundances for all m/z ratios vs the retention time. Multiple chromatographic peaks indicate elution of numerous compounds.
