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<br />ACZ Laboratories, Inc. August 10, 2007 <br />Quality Assurance Plan Version 12 <br />SOPAD018.08.07.12 Page 50 of 96 <br />12.4 Radiochemistry Calculations <br />12.4.1 Activity <br />The results of radioactivity are typically reported in terms of activity per unit volume or mass. Units <br />are normally expressed in picocuries (pCi), which equal 2.22 disintegrations per minute (dpm). <br />Specific formulas to determine activity are in the SOP for each method. The general formula is as <br />follows: <br />C V Rnet V <br />(eXyXIXvXu) <br />Where: C = activity per unit volume (pCi/L) <br />R1Qr = net counts per minute <br />e = counting efficiency, cpm/dpm <br />y = chemical yield <br />i = ingrowth correction factor <br />v = volume or mass being counted (L) <br />u = units correction factor, 2.22 for cpm to pCi <br />12.4.2 Counting Error <br />Radiochemical data are considered incomplete without reporting associated random and systematic <br />errors. For this reason all radiochemical results should be accompanied by a counting error at the 95% <br />confidence level (1.96*standard deviation). The general counting error formula is as follows: <br />E _ 1.96(Ro / ti + B / t2) v2 <br />(e)(y)(i)(v)(u) <br />Where: E = counting error <br />Ro = gross sample, cpm <br />tj = sample count duration, min <br />B = background, cpm <br />tz = background count duration, min <br />e, y, i, v, and a are as previously defined. <br />12.4.3 Lower Limit of Detection (LLD) <br />LLD (also referred to as Minimum Detectable Activity or MDA) is considered the smallest quantity of <br />sample radioactivity that will yield a net count for which there is a pre-determined level of confidence <br />that radioactivity is present. At the 95% confidence level, the following equation calculates the LLD <br />for any single nuclide. The calculation uses the standard deviation for the background counting rate, <br />assuming the sample and background counting rates should be very similar at the LLD. The formula <br />for determining LLD is as follows: <br /> <br /> <br /> <br />i <br /> <br />L , -7 <br /> <br /> <br /> <br /> <br />t <br />1 <br />r <br /> <br /> <br />2773 Downhill Drive 970-879-6590 ' <br />Steamboat Springs, CO 80487 www.acz.com <br />1