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Pesticides/PCBs Method TO-10A <br /> 12.6.7 Adjust to final volume by carefully rinsing needle tip and concentrator tube well with solvent(usually <br /> n-hexane). <br /> 13. Calculations <br /> 13.1 Determination of Concentration <br /> 13.1.1 The concentration of the analyte in the extract solution can be taken from a standard curve where peak <br /> height or area is plotted linearly against concentration in nanograms per milliliter (ng/mL). If the detector <br /> response is known to be linear, a single point is used as a calculation constant. <br /> 13.1.2 From the standard curve,determine the nanograms of analyte standard equivalent to the peak height <br /> or area for a particular compound. <br /> 13.1.3 Ascertain whether the field blank is contaminated. Blank levels should not exceed 10 ng/sample for <br /> organochlorine pesticides or 100 ng/sample for PCBs and other pesticides. If the blank has been contaminated, <br /> the sampling series must be held suspect. <br /> 13.1.4 Quantity of the compound in the sample(A)is calculated using the following equation: <br /> AS x Ve <br /> A - 1000 <br /> V. <br /> i <br /> where: <br /> A= total amount of analyte in the sample,ng. <br /> A,= calculated amount of material injected onto the chromatograph based on calibration <br /> curve for injected standards,ng. <br /> Ve= final volume of extract,mL. <br /> V;= volume of extract injected,µL. <br /> 1000= factor for converting microliters to milliliters. <br /> 13.1.5 The extraction efficiency(EE)is determined from the recovery of surrogate spike as follows: <br /> EE(%) = I S I [100] <br /> S, <br /> where: <br /> EE= extraction efficiency,%. <br /> S= amount of spike recovered,ng. <br /> Sa= amount of spike added to plug,ng. <br /> The extraction efficiency(surrogate recovery)must fall between 60-120%to be acceptable. <br /> 13.1.6 The total volume of air sampled under ambient conditions is determined using the following equation: <br /> January 1999 Compendium of Methods for Toxic Organic Air Pollutants Page 10A-13 <br />