Fractionation, gradient elution

Systems with different selectivity were nsed for the separation of 10-deacetyl-baccatin III (10 DAB 111) from yew extracts [69]. A silica column with stepwise gradient elution with aqneous methanolic mobile phases can be nsed for separation of the taxoid fraction from nonpolar materials, partial separation of the taxoid fraction into a polar one (containing 10-DAB 111), and for a medinm polarity taxoid fraction (containing paclitaxel and cephalomannine). Most polar material (tannins... 

Wade, H. E., The fractionation of phosphate esters on ion-exchange resin by a new system of pH-gradient elution, Biochem.., 77, 534, 1960. 

HPLC fractionation is the first step (dimension) in the two-dimensional analysis of complex peptide mixtures. This step is generally carried out by gradient elution... 

Fig. 39.3 LC PDA analysis, UV (297 nm) trace (using 1 mL/min gradient elution from 90% H20/MeCN (0.01% TFA) to MeCN (0.01% TFA) over 30 minutes followed by a 5 minute flush with MeCN on a Phenomenex Onyx CiglOO x 4.6mm column) showing a) non-polar, b) intermediate, c) polar fractions and d) characteristic absorbance profile of parotoid secretion from B. marinus.

The Fractionation of Polyisobutene by Gradient Elution, C.J. Panton, P.H. Plesch and P.P. Rutherford, Journal of the Chemical Society, 1964, 2586-2591. 

Preparative and analytical HPLC were carried out in an ODS column using gradient elution. The gradient was composed of methanol, water and formic acid. The chemical structures of the new pigments were elucidated by UV-VIS, 2D NMR and LC-MS. MS conditions were capillary 3 kV, cone 30 and 60 V, extractor 7 V, sources block temperature 120°C, desolvation temperature 150°C [257],The chromatographic profile of the SEC fraction containing the new pigments is shown in Fig. 2.116. The chemical structures of the new derivatives identified by various spectroscopic techniques are shown in Fig. 2.117. 

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