You wish to measure the concentration of methyl benzoate in a plant stream by ga

Question

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 tight involved a solution containing 1.77 mg/mL of methyl benzoate (peak A) and 1.95 mg/mL of butyl benzoate (peak B). The area of peak A was determined to be 312 and of peak B to be 362 (measured in arbitrary units by the computer) To measure the sample. 1.00 mL of a standard sample of benzoate containing 2.59 mg/ml was mixed with 1.00 mL of the plant stream material, and analysis of the mixture gave a peak area of 471 for peak A and 421 for peak B. What is the concentration of the methyl benzoate in the plant stream?

Explanation / Answer

From the data for peak A and peak B

First calculate response factor for methyl benzoate to butyl benzoate standard

response factor = (312/1.77)/(362/1.95)

                          = 0.95

then from the unknown plant stream solution

conc.(methyl benzoate) = 471 x 1.295/0.95 x 421

                                      = 3.050 mg/ml in 1 ml of original plant solution

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