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f <br /> C. Metals Analysis <br /> Most metals analyses are done by one of three techniques: <br /> flame atomic absorption spectrophotometry (FAA) , graphite <br /> furnace atomic abZOrption spectrophotometry (GrAA) , or <br /> inductively coupled argon plasma emission spectrophotometry <br /> (ICP) . Available supplementary techniques include cold <br /> vapor and hydride generation. All sample digestions follow <br /> EPA. or Standard Methods prescribed procedures. A daily <br /> method blank is run for each element. A three-point <br /> calibration curve is determined daily for each elemen . <br /> Calibration standards for that curve are prepared by fresh <br /> dilution. of 1000 mg/L certified standards obtained from <br /> commercial sources. <br /> a When the concentration of the metal being determined <br /> exceeds the highest standard, the sample is diluted so it <br /> falls witain the range of calibration. A daily laboratory <br /> control standard, generally obtained from the USEPA, is run <br /> for metals determined by GFAA. The accuracy of the <br /> analysis of metals in soils is checked periodically by <br /> analyzing a National Bureau of Standards reference material <br /> such as SRM #1646, an estuarine sediment. <br /> D. Selected General ChemistrProcedures <br /> ! -- — <br /> I } 1. Biochemical Oxygen Demand (BOD) <br /> Samples for five-day BCD are stored at 4 degrees C and <br /> set within 48 hours of receipt. To test the quality of <br /> the dilution water, its dissolved oxygen is measured <br /> initially and at the end of the five-day incubation <br /> period. Three dilutions of each sample are set. The <br /> oxygen depletion of at least one of the dilutions must <br /> be at least two mg/L; the final dissolved oxygen con- <br /> tent must be greater than one mg/L. One duplicate and <br /> one glucose--glutamic acid laboratory control standard <br /> are set with each batch of samples. Fresh BOD seed in <br /> the form of settled primary effluent from a municipal <br /> wastewater treatment facility is obtained weekly. Seed <br /> material for analysis of industrial samples is also <br /> 1 <br /> available. <br /> 2. General Mineral Analysis <br /> Several checks on the accuracy of the analysis of <br /> drinking water for general minerals are applied. The <br /> `.; anion-cation balance must agree to within */- 3%. <br /> Also, the total dissolved solids content should fall <br /> within 65 to 75% of the specific conductance. <br /> vI-2 <br />