Читать книгу Process Gas Chromatographs - Tony Waters - Страница 35

Your instructor will provide the answers to these test questions.

1 S1. In gas‐liquid chromatography, what is the physical state of the mobile phase?Select the one best answer:GasGas or liquidLiquidSolid

2 S2. In gas‐liquid chromatography, what is the physical state of the stationary phase?Select the one best answer:GasGas or liquidLiquidSolid

3 S3. In gas‐liquid chromatography, what is the physical state of the injected sample?Select the one best answer:GasGas or liquidLiquidSolid

4 S4. According to the chapter text, what is a typical number of analyses done per day by a process gas chromatograph, relative to the number done by a laboratory gas chromatograph?Select the one best answer:About 80 times as manyAbout 120 times as manyAbout 240 times as manyAbout 720 times as many

5 S5. According to the chapter text, what is the main function of a housekeeping column?Select the one best answer:To separate all the measured components.To separate only the unmeasured components.To allow strongly‐retained components to quickly exit the column system.To permanently absorb one or more unmeasured components.

6 S6. Imagine you are changing a PGC from liquid sample injection to gas sample injection and the gas sample will be at atmospheric pressure. If the previous liquid sample volume was 1 μL, what new gas sample volume would you install to get about the same peak heights?Select the one best answer:0.001 mL0.3 mL0.9 mL3.0 mL

7 S7. PGC detectors may not respond to every analyte. Consider the statements below; which statements are correct?Select all of the correct statements and none of the incorrect statements:No detector can respond to hydrogen sulfide, H2S.The thermal conductivity detector does not respond to hydrocarbons.The flame ionization detector is very sensitive and can measure low concentrations of carbon dioxide, CO2.The flame photometric detector does not respond to carbon monoxide, CO.

8 S8. What is a chromatogram, and why is it important?From the list below, select all the correct statements and none of the incorrect statements:The chromatogram is a graphical plot of the detector signal against elapsed time.On a chromatogram, the horizontal axis represents elapsed time, which always increases from left to right, with the zero‐time marker on the far left.On the chromatogram from a modern process gas chromatograph, the vertical axis represents the concentration of the analytes and is scaled from zero to 100 %.Chromatographic faults produce symptoms visible on the chromatogram that an expert user can diagnose.

9 S9. How is each analyte peak on the chromatogram measured?From the list below, select all the correct statements and none of the incorrect statements:Most modern PGCs measure the peak height, but a few measure the peak area.To calculate the concentration of an analyte, the PGC multiplies the analyte peak height or peak area by a stored calibration factor.The calibration factor depends on the detector in use but is the same for each analyte in the sample.The calibration factors come from the analysis of a calibration sample containing known concentrations of the analytes.