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    Reversed-phase liquid chromatography

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    A mixture of organic acids was separated by reversed-phase liquid chromatography. The data obtained for the chart recording were as follows: For acid A, the peak appeared 22 cm after injection with a full width at baseline of 8 cm. For acid B, the peak appeared 34 cm after injection with a full width at baseline of 6 cm. A non-retained compound generated a peak that appeared 4 cm after injection. The mobile phase flow rate in the column was 20 mL/min. The recorder chart speed was 5 cm per minute. Last, the column was 32 cm in length. Calculate:

    a. The adjusted retention time for peak A
    b. The capacity factor for peak A
    c. The resolution of compounds A and B.
    d. The number of theoretical plates in the column for acid B.
    e. The height equivalent to a theoretical plate for acid B

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    Solution Preview

    a. The adjusted retention time for peak A

    The term (tr - to) is called the adjusted retention time. First, we need to convert the lengths given into time. We know that the test ran at 5 cm per minute, which gives us:

    A: 22/5 = 4.4 min

    The unrelated compound ran 4 cm, giving us 4/5 = . 8min

    Thus we have

    (tr - to) = 4.4-.8 = 3.6 min

    b. The capacity factor for peak A

    k'x = (tr - to) / to = 3.6/ 0.8 =4.5

    c. The ...

    Solution Summary

    This solution helps with finding resolutions, number of plates, and equivalent heights for two acids.

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