In reversed phase liquid chromatography (RP-LC), the validity of a multiparametric (MP) non-linear least-squares regression iterative method has been evaluated for 14 different aqueous mobile phases modified with one, two or three organic solvents [acetonitrile (ACN), methanol (MeOH), or tetrahydrofuran (THF)] for calculating the retention time of unretained compound t M and the regression parameter (slope b), based on the use of alkan-2-ones and alkyl aryl ketones homologous series. The determination of t M and b has been studied for eight binary (ACN-H 2 O or MeOH-H 2 O), 3 ternary (ACNMeOH-H 2 O) and 3 quaternary (ACN-MeOH-THF-H 2 O) mobile phase systems on an Omnispher C 18 column. The multiparametric calculated t M and b values were compared with those obtained by Guardino's, and Grobler's methods. The MP retention indices (RI) of ten monosubstituted benzenes with different functionality (hydroxyl, carbonyl, nitro, etc.) based on the alkan-2-ones retention index standards have been determined and compared for the different mobile phase compositions studied. The influence of organic modifier type, the nature of mobile phase system and water content on the variation of retention parameter studied in this work were discussed.Keywords Reversed phase-liquid chromatography Á Binary, ternary and quaternary eluent systems Á Multiparametric least-squares adjustment Á Retention time of unretained compound and Retention indices Á Homologous series and monosubstituted benzenes
In reversed-phase liquid chromatography (RPLC), the comparison of experimental results obtained from different columns is a complex problem. A correspondence factor analysis (CFA) and a linear solvation energy relationship (LSER) were applied on retention data to characterize second-order intermolecular interactions responsible for retention on a set of RPLC columns. Seven octadecyl-C 18 columns with different packing materials are obtained from different manufacturers and one octyl-C 8 column. The retention data were determined under isocratic conditions using a methanol-water (65:35, v/v) mobile phase. The chromatographic retention indices based on alkan-2-ones and alkyl aryl ketones retention index scales are calculated using a multiparametric least-squares regressions iterative method. The CFA and LSER results permitted to highlight that the retention indices were appropriate for studying the second-order retention mechanisms on the eight chromatographic systems investigated and exhibited the best reproducibility. Although many earlier studies have reported the use of chemometric methods to characterize chemical factors affecting retention in RPLC using retention factors as retention parameters, this is the first study based on retention indices.
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