title: Determining orthogonal chromatographic systems prior to the development of methods to characterise impurities in drug substances.
abstract: To define starting conditions for the development of methods to separate impurities from the active substance and from each other in drugs with an unknown impurity profile, the parallel application of generic orthogonal chromatographic systems could be useful. The possibilities to define orthogonal chromatographic systems were examined by calculation of the correlation coefficients between retention factors k for a set of 68 drugs on 11 systems, by visual evaluation of the selectivity differences, by using principal component analysis, by drawing color maps and evaluating dendrograms. A zirconia-based stationary phase coated with a polybutadiene (PBD) polymer and three silica-based phases (base-deactivated, polar-embedded and monolithic) were used. Besides the stationary phase, the influence of pH and of organic modifier, on the selectivity of a system were evaluated. The dendrograms of hierarchical clusters were found good aids to assess orthogonality of chromatographic systems. The PBD-zirconia phase/methanol/pH 2.5 system is found most orthogonal towards several silica-based systems, e.g. a base-deactivated C16 -amide silica/methanol/pH 2.5 system. The orthogonality was validated using cross-validation, and two other validation sets, i.e. a set of non-ionizable solutes and a mixture of a drug and its impurities.
authors.affiliation: Department of Pharmaceutical and Biomedical Analysis, Pharmaceutical Institute, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Van Gyseghem
authors.forename: S
authors.initials: S
authors.lastname: Van Hemelryck
authors.forename: M
authors.initials: M
authors.lastname: Daszykowski
authors.forename: F
authors.initials: F
authors.lastname: Questier
authors.forename: D L
authors.initials: DL
authors.lastname: Massart
authors.forename: Y
authors.initials: Y
authors.lastname: Vander Heyden
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004364:Pharmaceutical Preparations / Q000302:isolation & purification*; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004364:Pharmaceutical Preparations