Sapling Learning macmitan learning A researcher was attemping to quantify the am

Question

Sapling Learning macmitan learning A researcher was attemping to quantify the amount of DDT (dichlorodiphenyltrichloroethane) in spinach with gas chromotography using a chloroform internal standard. To begin, the researcher examined a sample containing 8.03 mg/L DDT standard and 1.80 mg/L chloroform as the internal standard, producing peak areas of 2593 and 12079, respectively en, the researcher collected 5.97 g of spinach, homogenized the sample, and extracted the DDT sing an established method (assume 100% extraction), producing a 3 43 mL volume of unknown sample. The researchar then prepared a sample that contained 1.00 mL of the unknown sample and 1.50 mL of 12.54 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was for the unknown and chloroform respectively. Calculate the DDT concentration in the spinach sample. Express the final answer as miligrams DDT per gram of spinach

Explanation / Answer

Estimation of amount of DDT in the sample

Response factor (F) = (area of DDT/concentration of DDT)/((area of chloroform/concentration of chloroform)

From the first measurement we get,

response factor (F) = (2593/8.03 mg/L)/(12079/1.80 mg/L)

                               = 0.05

For spinach sample analysis,

concentration of chloroform in the solution = 12.54 mg/L x 1.5 ml/25 ml = 0.7524 mg/L

So using response factor equation,

0.05 = (6249/concentration of DDT in unknown)/(11635/0.7524)

concentration of DDT in 25 ml solution = 8.082 mg/L

concentration of DDT in 1.0 ml solution = 8.082 mg/L x 25 ml/1 ml = 202.05 mg/L

Concentration of DDT in 3.43 ml solution = 202.05 mg/L x 3.43 ml = 693.0315 mg/L

DDT concentration in spinach sample = 693.0315 mg/5.97 g = 116.086 mg DDT/g spinach sample

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