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 6.44 mg/l ddt standard and 1.41 mg/l chloroform as the internal standard, which produced peak areas of 3979 and 9257 for the ddt and chloroform, respectively. a. determine the response factor (f).