The Contractor shall use proven instruments and techniques to identify and measure the concentrations of volatile, semivolatile, and pesticide compounds listed on the Target Compound List (TCL). The Contractor shall employ state-of-the-art GC/MS and/or GC/EC procedures to perform all analyses, including the necessary preparations for analysis. The EPA provides the Contractor with the specific analytical procedures to be used and defines the specific application of these procedures to this contract. For volatiles and semivolatiles, this includes instructions for sample preparation, gas chromatographic screening, mass spectrometric identification, and data evaluation. Specific ions used for searching the mass spectral data for each compound are included. For pesticides, this includes instructions for sample preparation, gas chromatography, confirmation of identification by gas chromatography and/or mass spectrometry, and data evaluation.