Evaluation of several global resolution functions for liquid chromatography

An interpretative approach, that makes use of the overlapped fraction of ea ch chromatographic peak as elementary resolution criterion, was applied to the separation of mixtures of compounds. The elementary resolution measurem ents for all peaks in the chromatogram were reduced to a single numerical v alue using several functions: normalised by the mean resolution product, un normalised product, geometrical mean of the unnormalised product, and worst elementary resolution value. The descriptive capability of these reduction functions was evaluated through the observation of global resolution diagr ams and the change in the shape of the chromatograms in the selected factor space. MICHROM, a software program which permits the reliable simulation a nd optimisation of mobile phase composition, was used for this task. Among the four functions, the unnormalised product offered the best resolution me asurements in agreement with the chromatographer judgement. The methodology is illustrated with three mixtures: six thiazide diuretics, three diuretic s and five beta-blockers, and seven fluorescent diuretics, eluted with mice llar mobile phases of sodium dodecyl sulphate without and with 1-propanol. The conclusions are equally valid for other chromatographic modes. (C) 1999 Elsevier Science B.V. All rights reserved.