Figure 1.

Initial contaminant identification criteria. RT = retention time. Identities of selected compounds were then confirmed with authentic standards. Good match = 1) For halogenated compounds, the halogenated isotopic clusters should match those in the corresponding library mass spectrum, and loss of halogen must be observed in the mass spectrum. For non-halogenated compounds, the pattern (m/z values and relative abundances) of the 3 most prominent ions should match that of the corresponding library mass spectrum.