The Chromatogram

A typical gas chromatogram is shown at right. The initial time of the sample injection is denoted t0. After a specific amount of time (known as the retention time tr1 = t1-t0, ) the solvent emerges from the column followed by the three sample components in order of increasing boiling point temperature. The respective retention times can be compared to retention times of known samples to enable identification of the unknown sample components.

The area beneath each peak can be used to determine the percentage of a given component in the total sample mixture. In the olden days, each peak was cut out and then weighed on a balance to determine peak area. Today, electronic integrators calculate peak areas automatically.