Application of hollow fiber membrane mediated with titanium dioxide nanowire/reduced graphene oxide nanocomposite in preconcentration of clotrimazole and tylosin.

In this paper, TiO2 nanowires and TiO2 nanoparticles have been successfully anchored on graphene oxide (GO) nanosheets by a facile one-step hydrothermal method. The synthesized TiO2 NWs/RGO and TiO2 NPs/RGO nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. After comparatively studying of the as-made nanocomposites, TiO2 NWs/RGO nanocomposite showed the best adsorbing performance and applied as an attractive efficient sorbent reinforced with microporous hollow fiber membrane through the sol-gel technology. In the following, the selected nanocomposite was utilized for simultaneous preconcentration and determination of clotrimazole and tylosin using high performance liquid chromatography (HPLC)-UV detection, respectively. In order to optimize the extraction conditions through affecting parameters (pH, stirring rate, salt addition, extraction time and volume of donor phase), response surface methodology (RSM) was employed as a powerful statistical technique. Under the optimal conditions, the limit of detection (S/N=3) of proposed HFSPME method, was 0.67 µg L(-1) for clotrimazole and 0.91 µg L(-1) for tylosin with good linear ranges of 1.7-8000.0 µg L(-1) and 4.0-6000.0 µg L(-1). The inter-day and intra-day relative standard deviations (RSD%) at 100 µg L(-1) concentration level were in the ranges of 2.10-3.58% for clotrimazole and 3.45-7.80% for tylosin (n=5), respectively. The proposed microextraction device was extended for determination of ultra trace amounts of target analytes in milk and urine samples with satisfactory results.

Application of capillary zone electrophoresis with off-line solid-phase extraction to in vitro metabolism studies of antifungals.

A simple and robust solid-phase extraction (SPE) procedure for the cleanup and sample preconcentration of antifungals (ketoconazole, clotrimazole, itraconazole, fluconazole, and voriconazole) and their metabolites after incubation with human liver microsomes, as well as a simplified capillary zone electrophoresis (CZE) method for their rapid analysis, have been developed to determine the stability of these compounds in in vitro samples. Three different sample pretreatment procedures using SPE with reversed-phase sorbents (100 mg C8, 100 mg C18, and 30 mg Oasis-HLB) were studied. The highest and most reproducible recoveries were obtained using a 30 mg Oasis-HLB sorbent and methanol containing 2% acetic acid as eluent. Enrichment by a factor of about four times was achieved by reconstituting the final SPE eluates to a small volume. For the CZE separation, good separations without interfering peaks due to the in vitro matrix were obtained with a simple running electrolyte using a fused-silica capillary. The best separation for all components originated by each tested drug after incubation with human liver microsomes (unmetabolized parent drug and its metabolites) was obtained using a 0.05 M phosphate running buffer (pH 2.2) without additives. The effect of the injection volume was also investigated in order to obtain the best sensitivity. Performance levels in terms of precision, linearity, limits of detection, and robustness were determined.

Comparison between micellar electrokinetic chromatography and HPLC for the determination of Betamethasone Dipropionate, Clotrimazole and their related substances.

The complete separation of a composite mixture that consisted of Betamethasone Dipropionate (BMD), Clotrimazole and their derivatives in a pharmaceutical dosage form was achieved within 15 min using sodium dodecyl sulfate (SDS) micellar electrokinetic chromatography (MEKC). For the MEKC separations, electrophoretic media consisting of SDS-phosphate buffer and various concentrations of alcohols or acetonitrile were used. The optimal condition for separating BMD, Clotrimazole and their analogues was found to be 50 mM SDS-15% acetonitrile-5% butanol at pH 7.2. The results demonstrated that the method was valid for the quantitation of BMD, Clotrimazole and analogues with selectivity and precision comparable to that of High-Performance Liquid Chromatography (HPLC).