Gas chromatography mass spectrometry (GC-MS) enables the identification and quantification volatile and semi-volatile organic compounds at trace concentrations from complex mixtures. The technique pairs separation of compounds using gas chromatography with sample identification and quantification via mass spectrometry. GC-MS is a critical technique in a variety of disciplines including environmental science, biology, geology, and materials sciences. The EMES operates a Shimadzu QP2010 Ultra GC-MS within the Shimadzu Environmental Research Laboratory. The GC-MS is a single quadrupole system equipped with a split/splitless injector and an Rtx-5 (USP 27) column enabling analysis of a wide range of compounds.