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Chemistry LibreTexts

Chromatography

  • Page ID
    283291
  • Learning Objectives

    After completing this exercise, students will be able to:

    • Calculate the resolution of 2 peaks in a chromatographic experiment.
    • Use chromatographic data in a quantitative analysis.
    1. Compounds A and B are separated in a chromatographic system. The table below shows the retention times and peaks widths for each compound.  Determine if the peaks are separated enough to allow for quantitative analysis.

      Compound

      Retention time (min)

      Peak Width (min)

      A

      13.3

      0.86

      B

      14.1

      1.02

     

     

    1. Cinnamaldehyde is the component responsible for cinnamon flavor. It is also a potent antimicrobial compound present in essential oils.  The GC response of an artificial mixture containing six essential oil components and methyl benzoate as an internal standard is shown in the figure below.1

       

      1. An idealized enlargement of the region neat the cinnamaldehyde peak is given below. Determine the retention time and peak width for cinnamaldehyde.

         

         

         

         

      2. Quantitative data were obtained using methyl benzoate as the internal standard. The following results were found for calibration curves of cinnamaldehyde, eugenol and thymol.  The values under each component represent the peak are of the component divided by the peak area of the internal standard.  Determine the calibration curve equations for each component.  Include the R2 values.

        Concentration,
        mg sample/200 µL

        Cinnamaldehyde

        Eugenol

        Thymol

        0.50

        -

        0.4

        -

        0.65

        -

        -

        1.8

        0.75

        1.0

        0.8

        -

        1.10

        -

        1.2

        -

        1.25

        2.0

        -

        -

        1.30

        -

        -

        3.0

        1.50

        -

        1.5

        -

        1.90

        3.1

        2.0

        4.6

        2.50

        4.0

        -

        5.8

         

         

         

         

         

         

         

         

         

         

         

         

      3. For the data in in part (b), determine which of the components has the highest calibration curve sensitivity? Which has the lowest?


         
      4. A sample containing the three essential oils in part (b) gave peak areas relative to the internal standard area: cinnamaldehyde, 2.6; eugenol, 0.9; thymol, 3.8.  Determine the concentrations of each of the oils in the sample.

     

     

     

    Contributors and Attributions


    1Adapted from Skoog, D.A.; West, D. M.; Holler, F. J.; and Crouch, S. R.  Fundamentals of Analytical Chemistry, 9th ed.; Brooks/Cole, Cengage Learning:  Belmont, CA, 2014, p 910-911.

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