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Field Filtration of Samples <br />Samplers will refrain from filtering TOC, TOX or other organic compound samples as <br />the increased handling required may result in the loss of chemical constituents of <br />interest. Allowing the samples to settle prior to analysis followed by decanting the <br />sample is preferable to filtration of these substances. If filtration is necessary for the <br />determination of extractable organic compounds, the filtration should be performed in <br />the laboratory. It may be necessary to run parallel sets of filtered and unfiltered <br />samples with standards to establish the recovery of hydrophobic compounds when <br />sample must be filtered. All the materials' precautions used in the construction of the <br />sampling train should be observed for filtration apparatus. Vacuum filtration of <br />groundwater samples is not recommended. <br />Water samples for dissolved inorganic chemical constituents (e.g., metals, alkalinity <br />and anionic species) will be filtered in the field. <br />Sample Containers <br />Sample containers vary with each type of analytical parameter. Selected container <br />types and materials are non-reactive with the sample and the particular analytical <br />parameter being tested. Appropriate containers for volatile organics are glass bottles <br />of at least 40 milliliters in size fitted with teflon -faced silicon septa. Sample containers <br />are properly cleaned and sterilized by the certified laboratory according to the EPA <br />protocol for the individual analysis. <br />Sample Preservation and Shipment <br />Various preservatives are used by the certified laboratory to retard changes in <br />samples. Sample shipment from Ensco Environmental Services to laboratories <br />performing the selected analyses routinely occurs within 24 hours of sample <br />collection. <br />ENSCO ENVIRONMENTAL SERVICES, INC. <br />Laboratory Procedures <br />Latest Revision: May 15, 1989 <br />