Question

1. 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 7.92 mg/L DDT standard and 3.32 mg/L chloroform as the internal standard, which produced peak areas of 2919 and 11657 for the DDT and chloroform, respectively.

Determine the response factor (?).

2. After establishing the response factor of the instrument, the researcher collected 12.63 g of spinach, homogenized the sample, and extracted the DDT using an established method, producing a 3.62 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 1.00 mL of 11.49 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was analyzed using GCMS, producing peak areas of 6707 and 14291 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.