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caozeyuan

  • one year ago

What effect will the following factors have on a liquid chromatographic separation? (a) column not clamped in a perfectly vertical position; (b) very slow flow rate of the mobile phase; (c) collection of large elution fractions.

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  1. aaronq
    • one year ago
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    so for a), because the flow is caused by gravity alone, the tilt on the column will cause the sample to unevenly interact with the stationary phase, the largest effect will be on the longitudinal diffusion and bad separation overall.|dw:1443047221529:dw|

  2. aaronq
    • one year ago
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    b) will allow good equilibration between phases but large band broadening - you'll have a massive, dilute band to collect instead of a tight, concentrated band.|dw:1443047385789:dw|

  3. aaronq
    • one year ago
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    I'm entirely sure what they mean on c) but i can speculate that the large fractions collected will contain impurities, as well as dilute concentrations of the analyte of intererest - though this shouldn't be a problem if you can evaporate the solvent used but this is not always possible.

  4. caozeyuan
    • one year ago
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    Fantastic! Thank you so much!

  5. aaronq
    • one year ago
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    for a) you will probably saturate the stationary phase leading to problems in the equilibration - i.e. mass transfer effects

  6. aaronq
    • one year ago
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    no problem!

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