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Two methods are described for the determination of theophylline (THP) and ephedrine hydrochloride (EPH) in combined pharmaceutical tablet forms. The first method depends on the use of the first derivative of the ratio-spectra obtained by dividing the absorption spectrum of binary mixtures by a standard spectrum of one of the compounds. The first derivative amplitudes at 231.8 and 250.3 nm were selected for the assay of THP and EPH, respectively. Calibration graphs were established for 20–180 μg ml−1 for THP and 10–50 μg ml−1 for EPH. The second method is based on high-performance liquid chromatography on a reversed-phase column using a mobile phase of methanol–water (40+60,v/v) (pH 3) with detection at 217 nm. Linearity was obtained in the concentration range of 5–150 μg ml−1 for THP and 15–75 μg ml−1 for EPH. The detection limits for THP and EPH were 0.73 and 0.92 μg ml−1 by ratio-spectra derivative spectrophotometry and 0.59 and 0.86 μg ml−1 by HPLC, respectively. The proposed methods were successfully applied to the determination of these drugs in laboratory-prepared mixtures and in tablets. The relative standard deviations were found to be less than 1.5%, indicating reasonable repeatibility of both methods. [Copyright &y& Elsevier]

A reversed-phase high performance liquid chromatography (RP-HPLC) method with UV detection is described for the simultaneous determination of metronidazole and miconazole in pharmaceutical dosage forms. Chromatography was carried out on a C18 reversed-phase column, using a mixture of methanol–water (40+60, v/v) as a mobile phase, at a flow rate of 1.0 ml min−1. Sulfamethoxazole was used as an internal standard and detection was performed using a diode array detector at 254 nm. The method produced linear responses in the concentration ranges 10–70 and 1–20 μg ml−1 with detection limits 0.33 and 0.27 μg ml−1 for metronidazole and micanozole, respectively. This procedure was found to be convenient and reproducible for analysis of these drugs in ovule dosage forms. [Copyright &y& Elsevier]

In the present paper, an electrochemical method was developed for the determination of pterostilbene (a phenolic phytoalexin) using adsorptive anodic stripping voltammetry at a cathodically pretreated boron-doped diamond electrode. The oxidation of compound was irreversible and exhibited an adsorption controlled process which is of pH dependence. The sensitivity of the stripping voltammetric measurements was significantly improved in the presence of cationic surfactant, cetyltrimethylammonium bromide (CTAB). Using square-wave stripping mode, a highly linear analytical curve was obtained for pterostilbene determination in 0.1 M HNO 3 solution containing 2 × 10 −4 M CTAB at +0.78 V (vs. Ag/AgCl) (after 30 s accumulation at open-circuit condition). The process could be used in the range of 0.005–1.0 μg mL −1 (2.0 × 10 −8 –3.9 × 10 −6 M), with a detection limit of 0.0011 μg mL −1 (4.3 × 10 −9 M). The proposed method was successfully applied to measure the concentration of pterostilbene in the commercial dietary supplements, with results similar to those obtained using a HPLC method at 95% confidence level. As far as it could be verified, the proposed method is the first one based on the electrochemical investigation of pterostilbene. [ABSTRACT FROM AUTHOR]

Highlights: [•] The first report on the reduction and determination of testosterone by a voltammetric technique in surfactant media. [•] Usefulness of glassy carbon electrode without any modification (except adding cationic surfactant to the solution). [•] More improved sensitivity (detection limit of 1.18nM) over a previously reported voltammetric method. [•] Practical applicability by the direct assays of oil-based pharmaceuticals and urine samples. [ABSTRACT FROM AUTHOR]

Abstract: The two new mononuclear complexes were prepared by reacting symmetric Schiff base, containing pyrimidine rings and the metal chlorides of Pd(II) and Pt(II) in methanol. The mononuclear structure of the complexes was confirmed on the basis of elemental analyses, magnetic susceptibility, IR, UV–Vis, NMR, DTA/TGA and API-ES mass spectral data. The interaction of these metal complexes with fish sperm double-stranded DNA (dsDNA) was studied electrochemically based on the oxidation signals of guanine and adenine. Differential pulse (DP) voltammetry by using renewable pencil graphite electrode was employed to monitor the DNA interaction at the surface or in solution. The results indicate that Pd(II) and (Pt) complexes with Schiff base ligand having pyrimidine rings strongly interacted with DNA. [ABSTRACT FROM AUTHOR]