Page 29 - Modern Derivatization Methods for Separation Sciences

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induced fluorescence detector. The detection limit was 2 pg/injection of pravastatin with a He-Cd laser-
induced fluorescence detector, which was 20 times more sensitive than the conventional fluorescence
detection (Fig. 1.1.4).

For HPLC separation of DNS-ED-derivatized pravastatin, a column-switching technique was used to
remove excess reagents and by-products. The HPLC system was described elsewhere [5]. In this case, a
combination of two reversed-phase columns of different lipophilicity were employed: A C4 column was
used as a preseparation column (first column) to delete the major peaks derived from the reagents and
the plasma components, and a fraction containing derivatized pravastatin was introduced into the
analytical C18 column (second column). A comparison between the chromatograms obtained with the
ODS column

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