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Quantitative Gas Chromatography

Quantitative Gas Chromatography. Chem 2223 Lab Prep. Goals and Objectives. Goals To become familiar with basic methods of quantitative analysis by gas chromatography Specific Objectives

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Quantitative Gas Chromatography

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  1. Quantitative Gas Chromatography Chem 2223 Lab Prep

  2. Goals and Objectives • Goals • To become familiar with basic methods of quantitative analysis by gas chromatography • Specific Objectives • Use the standard additions technique to determine the identities and concentrations of the components in a mixture of volatile organic compounds

  3. Setup

  4. Solutes and Internal Standard

  5. Internal Standard Method • Description • In this approach, an internal standard is added to the sample, and the response from the analyte peak is compared to the internal standard. This approach corrects for minor variations in the injection volume. • Response Factor (RF) • The response factor accounts for differences in the detector response between the analyte and standard.

  6. Sample Chromatogram and Integration Report IS X AX = 27.01 AIS = 17.80

  7. Calibration Curve with Internal Standard • Standards • Each contains fixed mass of internal standard, various masses of std analyte • Calibration curve shows linear response. Slope = response factor* • Unknown • Add known amount of internal standard • Inject and measure Ax/Ais • Determine cx/cis for your unknown from calibration curve. Since cis is known, cx for your unknown is simply • cx = (cx/cis)cis *This expression for the response factor is not used directly in your calculations. The following expression which accounts for the intercept is more rigorous (in practice the intercept is very near zero). Calculations based on the calibration data do take the intercept into account.

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