Laserfiche WebLink
often cost effective in the lon'. term and ensure Baca <br /> reliability relative to cross-contamination. If transfer of <br /> equipment is necessary, sampling should proceed from the <br /> least contaminated to the most contaminated well, if the <br /> latter information is available before sample collection. <br /> Water samples should be collected in vials or containers <br /> specifically designed to prevent loss of volatile constitu- <br /> ents from the sample. These vials should be provided by an <br /> analytical laboratory, and preferably, the labcratory <br /> conducting the analysis. No headspace should be present in <br /> the sample container once the container has been capped. <br /> This can be checked by inverting the bottle, once the sample <br /> is collected, and looking for bubbles. Sometimes it is not <br /> possible to collect a sample without air bubbles, particu- <br /> larly if water is aerated. In these cases, the investigator <br /> should record the problem and account for probable error. <br /> Cooling samples may also produce headspace (bubbles) , but <br /> these will disappear once the sample is warmed for analysis . <br /> Samples should be placed in an ice chest maintained at 40C <br /> with blue ice (care should be taken to prevent freezing of <br /> the water and bursting of the glass vial) . A thermometer <br /> with a protected bulb should be carried in each ice chest. <br /> C. Surface water: Grab samples should be collected in appro- <br /> priate glass containers supplied by the laboratory. The <br /> sample should be collected in such a manner that air bubbles <br /> are not entrapped. Semisolid samples should be collected <br /> the same way. The collected samples should be refrigerated <br /> (blue ice, 40C) for transport and analyzed within 7 days of <br /> collection (14 days with preservatives) . <br /> -62- <br />