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  • Author: Aziz-Ur Rehman x
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Naureen Shehzadi, Khalid Hussain, Muhammad Islam, Nadeem Irfan Bukhari, Muhammad Tanveer Khan, Muhammad Salman, Sabahat Zahra Siddiqui, Aziz-Ur Rehman and Muhammad Athar Abbasi

Abstract

The study describes the development and preliminary validation of a simple reverse-phase chromatographic method for determination of a novel drug candidate, 5-[(4-chlorophenoxy) methyl]-1,3,4-oxadiazole-2-thiol (OXCPM), in bulk and stressed solution, in order to find out the intrinsic stability behavior of the compound. Isocratic elution was carried out at a flow rate of 1.0 mL min-1 through a Promosil C18 column maintained at 25 °C, using the mobile phase comprising acetonitrile and aqueous o-H3PO4 (pH 2.67) (1:1, V/V). Detection was performed at 258 nm. The response of the detector was linear in a concentration range of 1.25-50.00 μg mL-1 with the correlation coefficient of 0.9996 ± 0.0001. Cumulative intra-day, inter-day and inter-instrument accuracy (99.5 ± 1.0, 100.2 ± 1.0 and 100.3 ± 0.4 %, resp.) with RSD less than 5 % indicated that the method was accurate and precise. The resolution and selectivity factor (>2 and >1, resp.), particularly in copper metal- and dry-heat-stress solutions, depicted the selectivity of the method. OXCPM remained stable under hydrolytic (acidic and neutral pH, ≤ 37 °C), photolytic and moist heat stress conditions. Under alkaline conditions (hydrolytic and photolytic), polar products were formed that eluted very fast through the column (tR < 3.75 min). At room temperature, the compound was susceptible to oxidation by hydrogen peroxide and transition metals. The ionogram of most of the stress solutions indicated the presence of a product having m/z 256, which might be a result of N- or Smethylation or -SH oxidation. The results of the study indicate that the method is selective, sensitive and suitable to be used for determination of OXCPM in bulk and under stress conditions.

Open access

Syed Mansoor Ali, W. A. Farooq, M. R. Baig, M.A. Shar, M. Atif, S. S. Alghamdi, M. S. Algarawi, Naeem Ur-Rehman and Muhammad Hammad Aziz

Abstract

We have investigated the influence of Ag doping on zinc oxide thin films. Pure and Ag doped, preferentially oriented transparent zinc oxide thin films were prepared by sol gel technique on a glass substrate using diethyl amine as a stabilizer. The X-ray diffraction analysis revealed that the films with hexagonal wurtzite type structure were polycrystalline in nature with a preferred grain orientation in the 101 direction. The crystallite sizes decreased from 34 nm to 27 nm after silver doping. Both photoluminescence and optical transmission measurements showed that the band gap increased after the Ag doping. The structure and optical characterization studies clearly indicated the incorporation of Ag in ZnO. Hence, the observed increase in the optical band gap and decrease in crystallite size can be directly attributed to the effect of Ag ion incorporation into the ZnO lattice.