Detection and identification of a variety of chemicals including organophosphates, organochlorines, carbamates, industrial pollutants, polycyclic aromatics, aliphatic hydrocarbons, miscellaneous pesticides, some natural products and some drugs using gas chromatography – mass spectrometry (GC/MS). Samples are screened using multiple instrument libraries containing mass spectra for thousands of compounds. Positive identification of a suspect sample is made by comparing sample mass spectra with that of a certified reference standard.