Separation of isomeric naphthalenesulphonic acids by micro high-performance liquid chromatography with mobile phases containing cyclodextrin

Aromatic sulphonic acids are important dye intermediates and the determinat ion of the individual isomers after their preparation by sulphonation of th e parent aromatic hydrocarbon is important for the monitoring of the dye pr oduction process. For this purpose, either reversed-phase chromatography wi th mobile phases containing strong electrolytes as additives or capillary z one electrophoresis with working electrolytes containing cyclodextrins can be used to separate and determine not only individual sulphonation products with various numbers of sulphonic groups, but also various isomeric di- an d trisulphonic acids. However, the separation of some isomers using either of the two techniques is not fully satisfactory. In the present work, HPLC with mobile phases containing cyclodextrins was employed to improve previou sly achieved separations of aromatic sulphonic acids. Because of the high c ost of cyclodextrin, microcolumn HPLC with diode-array detection on the col umns prepared in laboratory by supercritical fluid packing technique was em ployed for this purpose. Capillary columns packed with various octadecyl si lica gel materials were compared and their stability and efficiency were fo und suitable for the separation of the compounds tested. The selectivity of separation of some isomers improved significantly with respect to the prev ious methods. Procedures were designed for separation and analytical contro l of technological processes producing dye intermediates. (C) 2000 Elsevier Science B.V. All rights reserved.