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 In HSCCC as in HPLC isocratic analysis only elutes a limited polarity window of compounds for each constant composition solvent choice, as shown in Slide 7. From this figure it will be noted that in isocratic analysis, increasing the eluent strength ( in this reverse phase application, a higher amount of methanol initially and then finally both methanol and isopropanol is added to the aqueous mobile phase ) to elute late eluting compounds causes early eluting compounds to co-elute and ultimately elute on the solvent front.

Progressively increasing the elution strength of the mobile phase relative to the stationary phase will in both gradient HSCCC and HPLC allow a much broader range of polarities to be examined in one chromatogram without the above problem. This is demonstrated in Slide 8, which compares the gradient elution of the same standards initially shown by isocratic elution with different strength mobile phases in Slide 7

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