Question

A researcher was attempting to quantify the amount of dichlorodiphenyltrichloroethane (DDT) in spinach with gas chromatography using a chloroform internal standard. To begin, the researcher examined a sample containing 7.88 mg/L DDT standard and 3.80 mg/L chloroform as the internal standard, producing peak areas of 3953 and 6281, respectively. Then, the researcher collected 9.16 g of spinach, homogenized the sample, and extracted the DDT using an established method (assume 100% extraction), producing a 3.24 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 12.94 mg/L chloroform, which was diluted to a final volume of 25.00 ml. The sample was analyzed using GCMS, producing peak areas of 6667 and 13791 for the DDT in the unknown and the chloroform, respectively. Calculate the DDT concentration in the spinach sample. Express the final answer as milligrams of DDT per gram of spinach. concentration of DDT: mg DDT/g spinich

Answer 1

Lue know that Resolving power = M om om es dilference's mass. = 499 -535.98 Hyea of analyte Signal(Ad) - F/Area of standard signal .concentration of analyte (3] Leonientration of stantos 3953 SongP ( semi) 501164 = F (1652189) F= 0.3034 The concentration of standard, [s] = 12.94 mg/Ly 1.75ML 25mL -0.405 mg/L For unknown mixture, = 0.3034 votos non

6667 .: LD: 4623-4) 21:44 mg 14 let's calculate the concentration co o.soome [x] = 1.44 mg/L x 25:00ML O. Sooml = 72 mg). =0:072 mg/mL Mass eso 3.24 m2 = (0,072 mg) my x 3,24mL = 0.233 mg DDT conontration - 01233mg DDT 9.169 20.0254 mg Dot lg spinach.