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0 <br />D (~ °, ` Ins <br />BOOiLCLIFFS L,QBORATORV DIVISIORI <br />1475 PINE GROVE ROAD <br />P.O. BOX 774018 <br />STEAMBOAT SPRINGS, CO 80477 <br />September 23, 1985 <br />Mr. Mike Ludlow <br />Getty Twentymile Coal Company <br />29515 Routt County Road k27 <br />P. O. Box 897 <br />Oak Creek, Colorado 80467 <br />Dear Mike: <br />_o_ _ ~_ <br />~+-~_I~~ r r~l ~ i~^I f11 <br /><•r:: .. <br />Llti~ `~L ~ i Lr~ + ~~ <br />13031 8796260 <br />TELEX 510~100~3860 <br />Per your request, enclosed is a copy of the EPA analytical method for Silver <br />by atomic absorption (AA) furnace technique from the EPA "Methods for <br />Chemical Analysis of Water and Wastes", EPA-600/4-79-000 (Revised, March <br />1983). <br />You will notice that the optimum concentration range for this method is 1 to <br />25 ug/1 or 0.001 to 0.025 mg/1. The detection limit is listed as 0.2 ug/1 or <br />0.0002 mg/l. ACZ IPlC. is able to obtain a slightly better detection limit of <br />0.1 ug/1 or 0.0001 mg/1. Our lower detection limit is due to the improved <br />instrumentation available presently as compared to those in 1978 when this <br />method was developed. <br />Our past sixteen analytical runs for Silver by AA-Furnace have produced the <br />following quality control data: <br />o EPA Standard Reference Sample Mean and Standard Deviations <br />EPA Value x = 5.1 ± 0.6 ug/1 vs. ACZ Value x = 5.0 ± 0.3 ug/1 <br />o ACZ Reagent Blank Samples Mean and Standard Deviations <br />(ACZ Value x = 0.0 0.1 ug/1) <br />