Walter Winkle

Applications of HPLC with evaporative light scattering detection in fat and carbohydrate chemistry

SummaryThe advantages of an evaporative light scattering detector in HPLC are demonstrated using the separation of α, ω-dicarboxylic and hydroxycarboxylic acids, alkyl glucosides and mono-, di- and triglycerides as examples. By using this detector reversed phase as well as normal phase gradient HPLC becomes possible for substances with no UV absorption.

Quantitative analysis in the V0 zone. A chromatographic approach by coupling HPLC with GPC

SummaryQuantitative HPLC methods for substances that elute in the vicinity of the V0 peak are often characterized by poor reproducibility and/or serious systematic errors. This contribution shows that the problem can be solved when a GPC-column is coupled with the HPLC-column; the substances assembled in the V0-Peak are developed into a new dimension (Retention volumes become shorter than V0) und thus a separation from the V0 zone is achieved.The method is used to determine polyglycol in aliphatic and aromatic nonionic surfactants with a degree of ethoxylation up to 80. The products have to be soluble in methanol/water in the proportions 80/20. Polyglycols with a molecular weight up to 7000 are separated by gel chromatography according to their degree of ethoxylation, so that the mean molecular weights (number and weight average) are additionally accessible. It is found that the degree of ethoxylation in polyethyleneglycol is greater than in the associated surfactant.