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This calculation has a number of steps. Only the final value is input for assess

ID: 530547 • Letter: T

Question

This calculation has a number of steps. Only the final value is input for assessment. For GC analysis, your sample solution is madeup by mixing 2 mL of water with 50 mu L of your unknown and 30 mu L of a 10 ppm internal standard. The response factor (F) has previously been determined to be 2.0. The GC analysis yields peak areas of 1080 for the unknown and 1330 for the internal standard. Calculate the concentration of the internal standard in the sample solution. Calculate the concentration of the unknown in the sample solution. What is the concentration of the analyte in the unknown in ppm?

Explanation / Answer

Response factor (F) = (area/concentration)unknown/(area/concentration)standard

let x be the concentration of unknown in solution

R = 2.0

then,

2 = (1080/(x ppm/2.05 ml)/(1330/(10 ppm/0.03 ml)

concentration of unknown in sample solution (x) = 277 ppm

concentration of analyte in unknown (ppm) = 277 ppm x 2.05 ml/0.05 ml = 11357 ppm

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