Comparison of the performance of Chromolith Performance RP-18e, 1.8-μm Zorbax Eclipse XDB-C18 and XTerra MS C18, based on modelling approaches

HPLC method for detecting prostaglandin F2α analogs in cosmetics: Optimization for chromatographic separation and sample preparation

Some prostaglandin F2α (PGF2α) analogs, including bimatoprost and tafluprost, are pharmaceutical substances known to cause specific abnormal reactions that promote eyelash growth. However, research on the simultaneous analysis of multiple PGF2α analogs using HPLC-UV or DAD techniques is limited. In this study, a high-performance liquid chromatography (HPLC) method was developed for the simultaneous analysis of 11 PGF2α analogs, optimizing both the analytical column and sample preparation method. Five columns with varying particle sizes, lengths, and packing types were compared to select the optimal analytical column. The separation efficiency of the columns was confirmed by comparing their chromatographic parameters, including retention time, resolution, number of theoretical plates, and height equivalent to a theoretical plate. Solid-phase extraction (SPE) was used to pretreat cosmetic samples, and the washing solvent and cartridge type for the SPE process were optimized. The established HPLC method was validated in terms of linearity, limits of detection and quantification, recovery, accuracy, and precision. The verified analytical method was applied to eyelash serums currently available in the market, and norbimatoprost was detected in one product. The HPLC method proposed in this study may help prevent the distribution of cosmetics containing illegal PGF2α analogs.

Characterization of bonded stationary phase performance as a function of qualitative and quantitative chromatographic factors in chaotropic chromatography with risperidone and its impurities as model substances

Numerous stationary phases have been developed with the aim to provide desired performances during chromatographic analysis of the basic solutes in their protonated form. In this work, the procedure for the characterization of bonded stationary phase performance, when both qualitative and quantitative chromatographic factors were varied in chaotropic chromatography, was proposed. Risperidone and its three impurities were selected as model substances, while acetonitrile content in the mobile phase (20-30%), the pH of the aqueous phase (3.00-5.00), the content of chaotropic agents in the aqueous phase (10-100 mM), type of chaotropic agent (NaClO₄, CF₃COONa), and stationary phase type (Zorbax Eclipse XDB, Zorbax Extend) were studied as chromatographic factors. The proposed procedure implies the combination of D-optimal experimental design, indirect modeling, and polynomial-modified Gaussian model, while grid point search method was selected for the final choice of the experimental conditions which lead to the best possible stationary phase performance for basic solutes. Good agreement between experimentally obtained chromatogram and simulated chromatogram for chosen experimental conditions (25% acetonitrile, 75 mM of NaClO₄, pH 4.00 on Zorbax Eclipse XDB column) confirmed the applicability of the proposed procedure. The additional point was selected for the verification of proposed procedure ability to distinguish changes in solutes' elution order. Simulated chromatogram for 21.5% acetonitrile, 85 mM of NaClO₄, pH 5.00 on Zorbax Eclipse XDB column was in line with experimental data. Furthermore, the values of left and right peak half-widths obtained from indirect modeling were used in order to evaluate performances of differently modified stationary phases applying a half-width plots approach. The results from half-width plot approach as well as from the proposed procedure indicate higher efficiency and better separation performance of the stationary phase extra densely bonded and double end-capped with trimethylsilyl group than the stationary phase with the combination of end-capping and bidentate silane bonding for chromatographic analysis of basic solutes in RP-HPLC systems with chaotropic agents. Graphical abstract ᅟ.

Comparing monolithic and fused core HPLC columns for fast chromatographic analysis of fat-soluble vitamins

HPLC stationary phases of monolithic and fused core type can be used to achieve fast chromatographic separation as an alternative to UPLC. In this study, monolithic and fused core stationary phases are compared for fast separation of four fat-soluble vitamins. Three new methods on the first and second generation monolithic silica RP-18e columns and a fused core pentafluoro-phenyl propyl column were developed. Application of three fused core columns offered comparable separations of retinyl palmitate, DL-α-tocopheryl acetate, cholecalciferol and menadione in terms of elution speed and separation efficiency. Separation was achieved in approx. 5 min with good resolution (Rs > 5) and precision (RSD ≤ 0.6 %). Monolithic columns showed, however, a higher number of theoretical plates, better precision and lower column backpressure than the fused core column. The three developed methods were successfully applied to separate and quantitate fat-soluble vitamins in commercial products.