Chromatogram

 

This is an example of a chromatogram from a wolf scat; you can see the biomarkers circled. These biomarkers represent the chemical fingerprint that identifies an individual, for example.

The x-axis represents the compensation volts; this is the amount of voltage needed to "balance" a chemical as it heads toward the detector in something similar to a cloud of gas. You could think of it this way - at zero compensation volts, the chemical is perfectly balanced in the middle of this cloud; in other words, it is neutral, and has no electric charge, either positive or negative.

The y-axis is the retention time. This is the amount of time a chemical takes to pass through a gas chromatographic column. Basically, larger molecules take longer to pass through a column compared to smaller ones. However, it is really the boiling point of a chemical that determines how long it takes to pass through the column, and in general, larger molecules have higher boiling points.

The colors represent the abundance of specific chemicals. The lighter blue areas on the blue background are abundances of chemicals, and the more light the blue, (some are even green), the more abundant the chemical. We refer to those light blue areas as peaks, and the amount of a chemical can be calculated by integrating the area under the peak.