A researcher was attempting to quantify the amount of dichlorodiphenyltrichloroethane (DDT) in spinach using gas chromatography mass spectrometry (GCMS). First attempts using external calibration proved difficult, as reproducibility 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 analyzed a sample containing 5.67 mg/L DDT standard and 1.84 mg/L chloroform as the internal standard, which produced peak areas of 4035 and 10177 for the DDT and chloroform, respectively. After establishing the response factor of the instrument, the researcher collected 11.53 g of spinach, homogenized the sample, and extracted the DDT using an established method, producing a 3.70 mL solution containing an unknown amount of extracted DDT. The researcher then prepared a sample for analysis that contained 1.00 mL of the unknown DDT solution and 2.00 mL of 10.25 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was analyzed using GCMS, producing peak areas of 6789 and 13221 for the DDT and chloroform, respectively. Calculate the amount of DDT in the spinach sample. Express the final answer as milligrams of DDT per gram of spinach. In the problem it states that you are doing an internal standard calculation. If you didnt had that information, notice that our analyte is DDT and our standard is Chloroform, analyte and standard are different, therefore this is an internal standard calculation. We reviewed in class how to do this calculation (please check slides) and obtain the amount of DDT (in mg/L in this case), however this problem is asking us to take our response in mg DDT/L and transform it to mg DDT / gram spinach. Try it and let me know if you have questions. A.) 0.0263 mg DDT/g spinach B.) 0.0421 mg DDT/g spinach C.) 0.0513 mg DDT/g spinach D.) 0.0632 mg DDT/g spinach
A researcher was attempting to quantify the amount of dichlorodiphenyltrichloroethane (DDT) in spinach using gas chromatography mass spectrometry (GCMS). First attempts using external calibration proved difficult, as reproducibility 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 analyzed a sample containing 5.67 mg/L DDT standard and 1.84 mg/L chloroform as the internal standard, which produced peak areas of 4035 and 10177 for the DDT and chloroform, respectively.
After establishing the response factor of the instrument, the researcher collected 11.53 g of spinach, homogenized the sample, and extracted the DDT using an established method, producing a 3.70 mL solution containing an unknown amount of extracted DDT. The researcher then prepared a sample for analysis that contained 1.00 mL of the unknown DDT solution and 2.00 mL of 10.25 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was analyzed using GCMS, producing peak areas of 6789 and 13221 for the DDT and chloroform, respectively.
Calculate the amount of DDT in the spinach sample. Express the final answer as milligrams of DDT per gram of spinach. In the problem it states that you are doing an internal standard calculation. If you didnt had that information, notice that our analyte is DDT and our standard is Chloroform, analyte and standard are different, therefore this is an internal standard calculation. We reviewed in class how to do this calculation (please check slides) and obtain the amount of DDT (in mg/L in this case), however this problem is asking us to take our response in mg DDT/L and transform it to mg DDT / gram spinach. Try it and let me know if you have questions.
A.) 0.0263 mg DDT/g spinach
B.) 0.0421 mg DDT/g spinach
C.) 0.0513 mg DDT/g spinach
D.) 0.0632 mg DDT/g spinach
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