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Improvements in stationary phase stability have been and remain a great task for research of new stationary phases. Metal oxide-based stationary phases appear as one of perspective alternatives to classical silica based stationary phases regarding to their similar effectiveness, different selectivity, different retention mechanism and mainly better chemical and thermal stability. In this study, the retention behaviour of ondansetron and its five pharmacopoeial impurities on TiO(2)-based reversed phase was investigated. The influence of buffer type, pH and concentration on retention was studied. Different types and amount of organic solvent in mobile phase were tested. The effect of temperature and flow rate on separation was investigated. The separation conditions were optimized and developed method validated. The retention parameters - retention time (t(R)), retention factor (k'), theoretical plate number (N), resolution between peaks due to nearby peaks (R(s)) and symmetry factor (A(s)) have been compared to parameters achieved on polybutadiene-coated zirconia column. The thermodynamic parameters of retention of analysed compounds - enthalpy, entropy and Gibbs free energy - were calculated and compared to those achieved on polybutadiene-coated zirconia column. This work proves similarity of retention behaviour of ondansetron and its five related compounds on zirconia-based and titania-based stationary phases and potential utilisation of polyethylene covered TiO(2)-based reversed stationary phase as an alternative to polybutadiene-coated ZrO(2) stationary phase in pharmaceutical analysis of ondansetron.

The method for the determination of biotin by high performance liquid chromatography (HPLC) coupled with coulometric detector is presented here. Chromatographic and detection conditions were tested. A LiChrospher 60RP-select B column (250 mm x 4 mm; 5 microm) and the mobile phase containing 0.24 mol/L aqueous solution of acetic acid and acetonitrile in the ratio 85:15 (v/v) were found as the most suitable. The flow rate was 1 mL/min and the injected volume of the sample was 20 microL. The hydrodynamic voltammogram of biotin was measured and according to obtained data the detection parameters were set--channel I 600 mV, channel II 900 mV, sensitivity 1 microA. The developed method has been validated. The calibration curve is linear in the range 15-3600 ng/mL, correlation coefficient is 0.9998, limits of detection and quantification are 5 and 15 ng/mL, respectively. Recovery of the spiked samples was 98.67% with R.S.D. 0.255% on average. The developed method has been successfully applied for determination of biotin in pharmaceutical preparations.

Zirconia-based stationary phases represent an interesting alternative to silica-based materials. Two zirconia-based stationary phases were studied as an option for use in drug analysis. The different properties of zirconia material, distinct from RP silica-columns, were employed for the development of a novel and rapid stability monitoring HPLC method. This method enables simultaneous control of possible degradation processes of active substance (ibuprofen) as well as antimicrobial excipients (methyl-and propylparaben). The separation of ibuprofen, its two main degradation products 2-(4-isobutyrylphenyl)propionic acid and 4-isobutylacetophenone, parabens, and 4-hydroxybenzoic acid as their degradation product was successfully accomplished on a Zr-CarbonC18 column using a mobile phase consisting of acetonitrile-phosphate buffer (pH 4.8)-propan-2-ol (27:56:17, v/v/v). Detection was performed at 258 nm and the analysis was completed within 17 minutes.

Glimepiride is a modern hypoglycaemic agent, which belongs to the group of sulfonylurea derivates. In this paper, simple, specific and accurate RP-HPLC method was developed in order to study decomposition of glimepiride under the hydrolytic stress conditions (acid, neutral, alkaline and oxidative). The best separation of glimepiride and its degradation products was achieved on reverse phase C18 column. The mobile phase was composed of acetonitrile-phosphate buffer (pH 3.5, 0.03 M) (48:52, v/v). Employing RP-HPLC method, five main degradation products were detected in the exposed samples. It was found that the susceptibility of glimepiride to hydrolytic decomposition increased in following manner: neutral condition < alkaline condition < acid condition < oxidative condition.