Map You wish to measure the concentration of methyl benzoate in a plant stream b

Question

Map You wish to measure the concentration of methyl benzoate in a plant stream by gas chromatography. You prepare a sample of butyl benzoate to use as an internal standard. A preliminary run, shown at the right involved a solution containing 1.23 mg/mL of methyl benzoate ak A) and 1.35 mg/mL of butyl benzoate (peak B). The area of peak was determined to be 338 and of peak B to be 403 (measured in arbitrary units by the computer). To measure the sample, 1.00 mL of a standard sample of butyl benzoate containing 2.69 mg/mL was mixed with 1.00 mL of the plant stream material, and analysis of the mixture gave a peak area of 437 for peak A and 407 for peak B. What is the concentration of the methyl benzoate in the plant stream? 10 15 5 Time (min Number conc methyl benzoate mg/mL O Previous & Give Up & View Solution O Check Answer Next Exit. Hint

Explanation / Answer

peak B = 403 / 1.35 = 298.5

peakA = 338/ 1.23 = 274.8

Response factor = Peak B/Peak A   

                           = 298.5 / 274.8

                           = 1.09

unknown :

peak B = 407 / 2.69 = 151.3

peak A = 437 / X

F = peak B / peak A

1.09 = 151.3 / (437 / X)

X   = 3.13

concentration methyl benzoate = 3.13 mg / mL

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