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10-28-1993 14 31 X303 490 1,522 ATI FT COLLINS P•07 <br /> • i <br /> 7.8 Select appropriate working standards and cdl pathlength according to the follooAng <br /> table of approsimate working ranges: <br /> Patlllet,ath ltlaRge <br /> 10 acct <br />' <br /> 50 inn+ 0.5-8 ins <br /> 100 nen 0.1-4 rng <br /> Calibrate the instrument for the appropriate ccUs using a series or working standar& <br /> (6 3 3) It is not necessary to add silica gel to the standards. Deteriatne At.orbanee <br /> ±firmly for cult solution at the absorbance masimv rn at about 2930 cin '. Prepue a <br /> calibration plot of absorbance vs.mg petroleum hydrocarbons per 100:x1 solution <br /> 7.9 After the silks gel has settled to the sample extract. fill a clean cell unth soluuon and <br /> determine the absorbance of the extract. If the absorbaswe exceeds 0 9 prepare an <br /> appmpnate dilution. <br /> ' NOTE& The possibility that the absorptive capacity of the silica gel has been exceeded <br /> can be toted at this point by adding another 3 0 g silica gel to the extract and repeating <br /> the treatment and determination <br /> 7.10 Detemine tate concentration of petroleum hydrocarbons in the extract by comparing the <br /> • response against tate calibration plot. <br /> E. Caku4tions <br /> E.1 Calculpte the petroleum hydrocarbons to the sampla using the formula: { <br /> m8/1 Oetreleum Hydrararbans 4 g—B <br /> where. <br /> • R atg of Petroleum Hydromrbnns as determined from the calibration plot(7.10). <br /> D extraet dilution factor,tf used <br /> _ V .. volume otsample.to liters <br /> a Precision and Accuracy <br /> 9.1 PracrJoe and accuracy data aro not available at this time. <br /> 1 <br /> • x18 I.3 <br /> t <br /> 4f <br />