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 5.96 mg/L DDT standard and 1.15 mg/L chloroform as the internal standard, producing peak areas of 4759 and 9405, respectively.
A) Using the above information, determine the response factor (F).
After establishing the response factor of the instrument, the researcher collected 8.55 g of spinach, homogenized the sample, and extracted the DDT using an established method (assume 100% extraction), producing a 3.47 mL volume of unknown sample. The researcher then prepared a sample that contained 0.500 mL of the unknown sample and 1.75 mL of 12.20 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was analzed using GCMS, producing peak areas of 6329 and 13127 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.
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 5.96 mg/L DDT standard and 1.15 mg/L chloroform as the internal standard, producing peak areas of 4759 and 9405, respectively.
A) Using the above information, determine the response factor (F).
After establishing the response factor of the instrument, the researcher collected 8.55 g of spinach, homogenized the sample, and extracted the DDT using an established method (assume 100% extraction), producing a 3.47 mL volume of unknown sample. The researcher then prepared a sample that contained 0.500 mL of the unknown sample and 1.75 mL of 12.20 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was analzed using GCMS, producing peak areas of 6329 and 13127 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.
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