Abstract: Tablets containing ergometrine maleate(I) were powdered and dissolved in the mobile phase [methanol - 0.01 M phosphate buffer - 2% Na acetate (pH 7) (1:4)] and subjected to flow injection analysis with amperometric detection with a Kel-F - graphite electrode at +0.85 V vs. silver - AgCl. The calibration graph was rectilinear for 1 to 20 µg mL-1 of I and the detection limit was 50 ng mL-1. The coefficient of variation were 1%, and the results agreed well with those obtained by the official USP method.

Abstract: A simple, rapid and sensitive HPLC method has been developed for the simultaneous determination of ramipril and hydrochlorothiazide in their dosage forms. Acetonitrile: sodium perchlorate solution (0.1 M) adjusted to pH 2.5±0.2 with phosphoric acid (46:54 v/v), was used as the mobile phase, at a flow rate of 1.5 ml/min. A supelcosil™ LC-8 column (5 µm), 15 cm x 4.6 mm i.d. was utilized as stationary phase. Detection was affected spectrophotometrically at 210 nm. Clobazam was used as an internal standard. The method was also applied for the determination of ramipril in the presence of its degradation products. Linearity ranges for ramipril and hydrochlorothiazide were 4.5-45 and 0.6-14 µg/ml, respectively. Minimum detection limits (S/N=2) obtained were 180 and 23 ng/ml for ramipril and hydrochlorothiazide, respectively. The proposed method was further applied to the analysis of tablets containing the two drugs, the percentage recoveries±S.D. (n=5) were 100.45%±0.63 and 99.55%±0.78 for ramipril and hydrochlorothiazide, respectively.

Abstract: A flow injection method is described for the determination of phenazopyridine hydrochloride, based on electrochemical oxidation at the glassy carbon electrode. The suggested method is highly specific and can be used to determine phenazopyridine HCl in the presence of most drugs commonly found in pharmaceutical dosage forms or administered therapeutically. Applying a constant potential of +950 mV vs Ag/AgCl/3.5 M KCl reference electrode, the calibration curve was linear in the 1-30 µg/mL range, with minimum detectability of 0.2 ng (signal-to-noise ratio 2). Good accuracy and precision were obtained when the method was applied to some dosage forms containing phenazopyridine HCl. Although automation was not used in this study, an automated system could be incorporated because the method uses the technique of continuous analysis in a flowing stream. A 1:1 mixture of methanol - aqueous phosphate buffer solution (pH 7) containing 2% of Na acetate was pumped (1.0 mL min-1) through an electrochemical cell equipped with a vitreous-carbon working electrode, a platinum auxiliary electrode and a silver - AgCl - 3.5 M KCl reference electrode. Portions (50 µL) of a solution of phenazopyridine hydrochloride in the methanol - aqueous phosphate buffer were injected into the flowing stream and the current was measured with an applied potential of +950 mV. The method was highly specific; the calibration graph was rectilinear in the range 1 to 30 µg mL-1 and the limit of detection was 0.2 ng. The coefficient of variation was 0.16 to 0.44%.