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Environmental <br /> FIELD SAMPLE FMTRATION <br /> PROCEDURES FOR FIELD SAMPLE FILTRATION <br /> The general procedures listed below are applicable for field filtration of water samples for <br /> subsequent analysis of dissolved analytes. The filtration unit's instruction manual should be <br /> consulted for specific operating procedures applicable to that unit. <br /> 1. In the field, place a disposable 0.45 micrometer (µm) filter in the filtration <br /> apparatus. <br /> 2. Place 10 to 15 ml of sample water in the filtration apparatus, apply vacuum, and <br /> discard the filtered solution. Repeat two additional times for a total of three pre- <br /> washes. <br /> • 3. Fill the apparatus with well-mixed sample water from the collection container and <br /> -apply vacuum. Filter a suitable volume of sample water to meet sample analytical <br /> needs. <br /> 4. If the filter becomes clogged, note the volume of filtrate, carefully release vacuum <br /> from the flask, and discard the unfiltered sample water contained in the flask. <br /> Replace the used filter with a clean filter and repeat Steps 2and 3 using a sample <br /> volume equal to the amount that was able to pass through the first filter. <br /> 5. If an extremely turbid sample water is encountered, repeat the procedures using a <br /> pre-filter (usually 3.0 µm) followed by 0.45 µm filtration. <br /> • <br /> CO2110 <br />