Mapc A researcher was attemping to quantify the amount of DDT (dichlorodi spinac
ID: 985648 • Letter: M
Question
Mapc A researcher was attemping to quantify the amount of DDT (dichlorodi spinach with gas chromotography using a chloroform internal standard. To begin, the researcher examined a sample containing 8.59 mg DDT standard and 1.60 mg/L standard, producing peak areas of 5101 and 10087, respectively orm as the internal homogenized the sample, and extracted the DDT Then, the researcher collected 13.08 g of s using an established method (assume 100% extraction), producing a 3.48 mL volume of unknown sample. The researcher then 1.00 mL of 10.15 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was analzed using GCMS, producing peak areas of 6189 and 14127 for the unknown and chloroform, respectively a sample that contained 0.750 mL of the unknown sample and Calculate the DDT concentration in the spinach sample. Express the final answer as milligrams DDT per gram of spinach Number mg DDT/g spinach Use the following relationship to first solve for the response factor, F, for the standard (DDT) and the internal standard (chloroform), where Ax and [X] are analye instrument response and concentration, respectively, and As and [Sl are the internal standard instrument response and signal, respectively Then, use the same equation to solve for the unknown DDT concentration. Remember to account for dilutions and express the answer as milligrams of DDT per gram of spinachExplanation / Answer
From the first equation:
Ax/X = F As/S solving for F:
F = S*Ax / X*As
F = 5101 * 1.60 / 10087 * 8.59 = 0.0942
Now, it's time to calculate the concentration of S with the unknown sample:
S = 10.15 * (1/25) = 0.406 mg/L
Using the same equation of F, but instead of solving for F, we will solve for X:
Ax/X = F As/S
X = Ax * S / F * As
X = 6189 * 0.406 / 0.0942 * 14127
X = 1.8882 mg/L
m of X = 1.8882 * 0.025 = 0.0472 mg
ratio = 0.0472 / 13.08 = 0.0036 mg/g
Hope this helps