Fakiha El-Taib Heakal

Optimizing parameters affecting electroless Ni-P coatings on AZ91D magnesium alloy as corrosion protection barriers

Magnesium alloys are materials difficult to plate due to their high reactivity. The surface passive layer formed in air or water must be first removed prior the plating process. Generally, it was shown that electroless Ni–P coatings on AZ91D alloy are directly related to its surface pretreatment parameters and the various plating conditions. Micro-image morphology and chemical composition of the different coats were characterized by SEM, EDX, XRF and XRD techniques. Electrochemical polarization, porosity and adhesion tests were also performed to study the corrosion resistance of the samples. The plating step was accomplished either after a zincating treatment or directly after the fluoride activation treatment using basic nickel plating bath. Successful direct EN coatings obtained are good corrosion barriers for AZ91D alloy in aggressive environments.

RP-HPLC Stability-indicating Method for Estimation of Irbesartan and Hydrochlorothiazide in Bulk and Pharmaceutical Dosage Form

Abstract A stability indicating RP-HPLC method was described and validated for the simultaneous determination of hydrochlorothiazide (HCTZ) and irbesartan (IRB) in combined pharmaceutical preparations. In this study, hydrochlorothiazide and irbesartan were degraded under different stress test conditions as recommended by the International Conference on Harmonization (ICH). The degraded samples were used to develop a stability indicating high performance liquid chromatographic method (HPLC) for hydrochlorothiazide and irbesartan determination. The two drugs were separated from their degradation products using a reversed phase (C18) analytical column and a mobile phase consisted of 50 mM potassium di-hydrogen orthophosphate:acetonitrile (55:45, V/V) buffer (pH 2.5). The instrumental settings were optimized at flow rate of 1.3 mL min−1, column temperature of 30 °C, detection wavelength of 210 nm and injection volume of 20 µL. The retention time of HCTZ and IRB was around 3 and 5.2 min, respectively. The method was validated for linearity, precision, accuracy, specificity, ruggedness and robustness. The results indicated that the described method was suitable for quantitative analysis of HCTZ and IRB in the presence of their degradation products formed under a variety of stress conditions. The proposed method was also applicable to the determination of stability of HCTZ and IRB drugs and was successfully used in quality control of bulk manufacturing and pharmaceutical preparations.