The lower chromatogram has a shorter run time because: D 3000- 2500- 2000- 1500- 1000- 500- 0 3000- 2500 2000 1500 1000 500- 10 min. The upper chromatogram was obtained under constant flow conditions The carrier pressure is increased to maintain constant flow during the temperature program O The carrier flow increases as the oven temperature increases O The upper chromatogram was obtained at a lower isothermal oven temperature Constant pressure GC separation 20 min. Constant flow GC separation

The lower chromatogram has a shorter run time because: D 3000- 2500- 2000- 1500- 1000- 500- 0 3000- 2500 2000 1500 1000 500- 10 min. The upper chromatogram was obtained under constant flow conditions The carrier pressure is increased to maintain constant flow during the temperature program O The carrier flow increases as the oven temperature increases O The upper chromatogram was obtained at a lower isothermal oven temperature Constant pressure GC separation 20 min. Constant flow GC separation

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter26: An Introduction To Chromatographic Separations

Section: Chapter Questions

Problem 26.1QAP

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A researcher was attempting to quantify the amount of dichlorodiphenyltrichloroethane (DDT) in spinach using gas chromatography mass spectrometry (GCMS). First attempts using external calibration proved difficult, as reproducibility and external standard agreement were poor. To overcome these problems, the researcher used the internal standard calibration method with chloroform as the internal standard. To begin, the researcher analyzed a sample containing 5.67 mg/L DDT standard and 1.84 mg/L chloroform as the internal standard, which produced peak areas of 4035 and 10177 for the DDT and chloroform, respectively. After establishing the response factor of the instrument, the researcher collected 11.53 g of spinach, homogenized the sample, and extracted the DDT using an established method, producing a 3.70 mL solution containing an unknown amount of extracted DDT. The researcher then prepared a sample for analysis that contained 1.00 mL of the unknown DDT solution and 2.00 mL of 10.25…
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