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(c) After analysis of 20 laboratory control samples, the following data are obtained. Calculate the mean, standard deviation, upper control limit (UCL), lower controllimit (LC). [6%1 upper warning limit (UWL) and lower warning limit (LWL). No. Conc. (mg/L) No. Conc. (mg/L) No. Conc. (mg/L) No. Conc, (mg/L) 1 2.01 6 1.94 11 1.99 16 1.95 2 1.99 7 1.98 12 2.04 17 2.05 3 1.97 8 2.03 13 2.00 18 1.98 4 2.04 9 2.05 14 1.99 19 2.03 5 1.96 10 1.96 15 1.96 20 2.02 WNL 0 - 0 in WRE Mean upper control limit (UCL) upper warning limit (UWL) lower warning limit (LWL) lower controllimit (LCL) Standard deviation
1. Below is the test procedure testing of lead in food sample. 1. Prepare calibration standards - 2, 10, 20, 40 and 100ppm lead in 2% nitric acid. 2. 2g sample is digested using 2% nitric acid and hydrogen peroxide by microwave digester. 3. Dilute the sample to 50ml using Di water 4. ICPAES analysis 5. A standard solution of different sources is used as a calibration check standard. 6. A CRM with certified value 2.01ppm is used as the laboratory control sample (LCS)