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 nght involved a solution containing 1.25 mg/mL of methyl benzoate (peak A) and 1.38 mg/mL of butyl benzoate (peak B). The area of peak A was determined to be 356 and of peak B to be 405 (measured in arbitrary units by the computer). To measure the sample, 1.00 mL of a standard sample of butyl benzoate containing 2.61 mg/mL was mixed with 1.00 mL of the plant stream material, and analysis of the mixture gave a peak area of 487 for peak A and 411 for peak B. What is the concentration of the methyl benzoate in the plant stream? Conc._methyl benzoate =

Explanation / Answer

The given type of aanylysis called the Single Point Internal Standard method.

Internal response factor (IRFSC) = (areaIS x amountSC) / (amount IS x area SC)

Here IS = Internal Standard(butyl benzoate), SC = Specific Compound of Interest(methy benzoate)

Internal response factor = (405 * 1.25 / (1.38 *356) =1.0305

Amount of specific compound = (amountIS x areaSC x IRFSC) / areaIS = (2.61 * 487 * 1.0305)/411 = 3.187 mg/mL

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