sapling earning A researcher was attemping to quantify the amount of DDT (dichlo

Question

sapling earning A researcher was attemping to quantify the amount of DDT (dichlorodiphenyltrichloroethane in spinach using gas chromotography mass spectrometry (GCMS). First attempts using external calibration proved diffucult, as reproducibilty and external standard agreement were poor. To overcome these problems, the researcher used the internal standard calibration method with chloroform as the internal standard. To begin, the researcher examined a sample containing 9.12 mg/L DDT standard and 1.64 mg/L chloroform as the internal standard, producing peak areas of 2803 and 11189, respectively. A) Using the above information, determine the response factor (F) Number F 0.045 After establishing the response factor of the instrument, the researcher collected 12.22 g of spinach, homogenized the sample, and extracted the DDT using an established method (assume 100% extraction), producing a 2.87 mL volume of unknown sample. The researcher then prepared a sample that contained 1.00 mL of the unknown sample and 2.00 mL of 10.57 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was analzed using GCMS, producing peak areas of 8033 and 11905 for the unknown and chloroform, respectively B) Calculate the DDT concentration in the spinach sample. Express the final answer as milligrams DDT per gram of spinach. Number mg DDT g spinach Previous 3 Give Up & View Solution Check Answer Next Exit Hint

Explanation / Answer

qtyX=qtyA×(MX/MA)peakA/peakX

       = (12.22*(354.49/119.38))/(11905/8033)

       = 24.48454 mg DDT / g spinach

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