An electrochemical sensing platform to determine tetrahydrozoline HCl in pure form, pharmaceutical formulation, and rabbit aqueous humor.

In the pharmaceutical industry, finding cost-effective and real-time analyzers that provide valid data is a good aim. The purpose of this work was to propose a link between the pharmaceutical industry and the recent innovations in solid-contact ion-selective electrodes (SC-ISEs) for the utilization of these electrodes as real-time analyzers to evaluate the concentration of tetrahydrozoline HCl in different matrices. The backbone of these new potentiometric sensors is the conjunction of calix[6]arene and (2-hydroxypropyl)-ß-cyclodextrin as molecular recognition elements and a network of multi-walled carbon nanotubes as a solid transducer material between an ionophore-doped PVC membrane and microfabricated Cu electrodes. The proposed sensors were optimized to determine tetrahydrozoline, and their performances were assessed according to the IUPAC recommendations. The proposed solid-contact sensors were compared with liquid contact sensors, and the former sensors were found to be better than the latter sensors in terms of durability, handling, and easier adaptation to industry with comparable sensitivity. The measurements were implemented using phosphate buffer (pH: 6). The best obtained linearity range was 1 × 10-2 to 1 × 10-7 M, and the best LOD was 1 × 10-8 M. The sensors with the best performance were successfully applied to determine tetrahydrozoline in a pharmaceutical eye preparation and rabbit tears. The obtained results were statistically compared to those obtained by the official method of analysis, and no significant difference was obtained. The eco-score of the method was assessed using the eco-scale tool and also compared with that of the official method. The proposed approach was validated according to the International Council for Harmonisation (ICH) guidelines.

Stepwise optimization and sensitivity improvement of green micellar electrokinetic chromatography method to simultaneously determine some fluoroquinolones and glucocorticoids present in various binary ophthalmic formulations.

A sensitive micellar electrokinetic chromatography method is presented to simultaneously quantify ofloxacin, gatifloxacin, dexamethasone sodium phosphate and prednisolone acetate. The method has the advantages of being rapid, accurate, reproducible, ecologically acceptable and sensitive. The electrophoretic separation utilized 20 mm borate buffer as background electrolyte with pH 10.0 ± 0.1 and 50 mm sodium dodecyl sulfate as a micelle forming molecule. A capillary tube (50 µm i.d., 33 cm) of fused silica was used and on-column diode array detection at 243 nm for dexamethasone sodium phosphate and prednisolone acetate, and 290 nm for ofloxacin and gatifloxacin. Various factors were optimized such as the background electrolyte (type, concentration and pH), addition of sodium dodecyl sulfate and its concentration, detection wavelength, applied voltage and injection parameters. The studied drugs were efficiently separated in 6.2 min, at 20 kV with high resolution. The greenness of the method was estimated using an eco-scale tool and the presented method was found to have excellent green characteristics. The method was validated in conformance with International Conference on Harmonization guidelines, with acceptable accuracy, precision and selectivity. The suggested method can be employed for the economic analysis of the four drugs in dissimilar binary combinations of eye drops saving solvents and chemicals.

A Two-Step Optimization Approach: Validated RP-HPLC Method for Determination of Gatifloxacin and Dexamethasone in Ophthalmic Formulation.

The growing technology of stationary phase chemistry has a great impact on the chromatographic system performance and analysis economics. In this context, a simple rapid reversed phase high-performance liquid chromatography method development is presented for the analysis of gatifloxacin (GFN) and dexamethasone sodium phosphate (DSP) in their ophthalmic formulation. A two-step optimization approach has been conducted using optimum chromatographic conditions as well as proper selection of stationary phase. The chromatographic separation was carried out using sodium phosphate buffer pH 3.0 ± 0.1 and acetonitrile 72:28 v/v, respectively, with flow rate 1 mL min-1 and simultaneous detection at 243 nm. Three different column technologies were investigated at the optimum set of the chromatographic conditions: Xbridge® bridged ethylene hybrid silica, Kinetex™ Core-Shell and the Onyx™ Monolithic stationary phase. The monolithic column has shown better chromatographic separation, based on system suitability testing as well as shorter analysis time and sensitivity. The proposed method was validated according to International Conference on Harmonization guidelines. The linearity was achieved for GFN and DSP in the range 0.58-120 µg mL-1 and 0.50-120 µg mL-1, respectively, with acceptable accuracy, precision and selectivity.