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V. Common Sampling Errors <br /> The following are common errors made during sampling that lead to inconsistent <br /> analytical results: <br /> • Failure to calibrate instruments <br /> • Lack of equipment maintenance <br /> Use of inappropriate sample containers <br /> Lack of QA samples to assure precision of sampling methods and <br /> laboratory analysis. <br /> Sample loss or leakage during shipping or handling due to improper <br /> packaging <br /> Mislabelling <br /> Poor field records <br /> L. Chain of Custody <br /> The purpose of chain of custody procedures is to be able to trace possession of a <br /> sample from the time it is collected until the analytical results are obtained by the <br /> laboratory. Chain of custody procedures are important when analytical results are <br /> introduced as evidence in a legal proceeding. <br /> A sample is in "custody" if: <br /> • It is actually in one's physical possession <br /> • It is in one's view <br /> It was in one's possession and it was secured so that it could not be <br /> tampered with. <br /> • It is kept in a secured area with access restricted to authorized personnel <br /> only. <br /> • It is placed in a container that is sealed with an official seal that will be <br /> broken when the container is opened. <br /> Chain of custody documentation includes, but is not limited to, the entries in the <br /> sampler's field notebook, the official seals on the sampling containers and the chain of <br /> custody record. The inspector needs to assure that the relationship between the physical <br /> sample and the related documentation is clear, complete, and accurate. The sample <br /> number, date and time of sampling, location and sample type, preservative used, analysis <br /> required, and sampler's initials should appear on all documents. <br /> 29 <br />