Aresearcher was attempting to quantify the amount of (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 mg/l ddt standard and mg/l chloroform as the internal standard, which produced peak areas of and for the ddt and chloroform, respectively. a. determine the response factor (f). after establishing the response factor of the instrument, the researcher collected g of spinach, homogenized the sample, and extracted the ddt using an established method, producing a ml solution containing an unknown amount of extracted ddt. the researcher then prepared a sample for analysis that contained ml of the unknown ddt solution and ml of mg/l chloroform, which was diluted to a final volume of ml. the sample was analyzed using gcms, producing peak areas of and for the ddt and chloroform, respectively. b. calculate the amount of ddt in the spinach sample. express the final answer as milligrams of ddt per gram of spinach. amount of ddt: