The determination of levofloxacin by flow injection analysis using UV detection, potentiometry, and conductometry in pharmaceutical preparations.

A flow injection analysis (FIA) using UV detection, potentiometry and conductometry for levofloxacin (LVF) are described in this study. The best solvent system was found to consist of 0.2 M acetate buffer at pH 3 having 10% MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 288 nm. The detection limit (LOD) and limit of quantification (LOQ) for FIA were calculated to be 3 x 10(-7) M (S/N = 3) and 1 x 10(-7) M (S/N = 10), respectively. In the analysis of tablets, the RSD values were found to be 0.83, 0.98 and 0.99 for FIA, potentiometric and conductometric methods, respectively.

Flow injection analysis of doxazosin mesylate using UV-detection.

A flow injection analysis (FIA) of doxazosin mesylate (DOX) using UV detection is described in this study. The best solvent system was found to be consisting of 0.1 mol l(-1) acetate buffer at pH 4 having 10%MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 365 nm. The calibration equation was linear in the range of 1.3 x 10(-5) to 6.4 x 10(-5) mol l(-1). Limit of detection and limit of quantitation were calculated to be 1.6 x 10(-6) and 4 x 10(-6) mol l(-1) with a RSD 1.27 and 1.16% (n=8), respectively. The proposed method was applied to the determination of DOX in the pharmaceutical preparations. The results were compared with those obtained from UV-Spectrophotometry. The results showed that there is a good agreement between FIA method and UV-Spectrophotometry. The validation studies were realised by the related applications and the results were evaluated statistically. According to the results, insignificant difference was observed between the methods.

Voltammetric determination of doxazosin in tablets using rotating platinum electrode.

This study describes the voltammetric behaviour of doxazosin molecule based on the oxidation on the surface of platinum electrode in the stationary and rotating conditions and determine doxazosin in the tablets by differential pulse technique at only rotating condition. The experiments were carried out in the supporting electrolyte consisting of 0.2 M KCl and 0.2 M buffer solution in 10% (v/v) ethanol. The effect of initial potential was investigated and no adsorption effect was observed during use of +500 mV. The influence of pH on the peak current and peak potential was examined and the most symmetrical peaks were obtained at 0.5 M H2SO4 for rotating conditions. In the rotation range of 50-1000 rpm and up to 1.0x10(-5) M doxazosin, the factor affecting the voltammetric current was diffusional. The effect of rate of potential was tested between 2 and 20 mV for the stationary condition and the character of current was found to be diffusional up to 3x10(-5) M concentration of doxazosin solutions. The voltammetric determination of doxazosin in tablets was realised in the optimum rotating system conditions and depending on the statistical evaluations, acceptable results were obtained. Therefore, the method proposed in this study is practical, sensitive and accurate for the analysis of doxazosin in the quality control laboratories.

FIA of sildenafil citrate using UV-detection.

A flow injection analysis (FIA) of sildenafil citrate (SLD) using UV detection is described in this study. The best solvent system was found to be consisting of 0.2 M phosphate buffer at pH 8 having 10% MeOH. A flow rate of 1 ml. min(-1) was pumped and active material was detected at 292 nm. The calibration equation was linear in the range of 1x10(-6)-5x10(-6) M. Limit of detection (LOD) and limit of quantitation (LOQ) were calculated to be 3x10(-7) and 8.9x10(-7) M with a R.S.D. 1.9 and 0.6% (n=7), respectively. The proposed method was applied to the determination of SLD in VIAGRA tablet, containing 50 mg active material. The results were compared with those obtained from UV-Spectrophotometry. The results showed that there is a good agreement between FIA method and the UV-Spectrophotometry. The validation studies were realised by the related applications and the results were evaluated statistically. According to the results, insignificant difference was observed between the methods.

Pulse polarographic (constant and increasing) determinations of doxazosin in pharmaceutical tablets.

The optimum conditions using DC polarography and the determination of doxazosin employing SIAP and SCAP polarographic techniques are described in this study. All the experiments were conducted in the supporting electrolyte consisting of 20% ethanol (v/v), 0.2 M KCl and 0.2 M acetate buffer at various pH values in order to examine the optimum conditions, and pH 3.5 for the determination of doxazosin. Well-defined curves were obtained in the pH range of 1.5-7.5. The system was diffusional and irreversible at pH 3.5. The calibration studies were performed by using SIAP and SCAP polarography and satisfactory results were observed for all techniques. Since the sensitivity of SIAP and SCAP techniques were higher than the others, the determination of doxazosin was performed in filtered and unfiltered tablet solutions containing 4 mg active material. In the analysis of a tablet, the relative standard deviations (Srel %) of the techniques are in the filtered solutions +/- 0.9 (SIAP), +/- 0.8 (SCAP) and in the unfiltered solutions +/- 0.7 (SIAP), +/- 0.8 (SCAP) and no interference was observed during the analysis. The determination methods proposed in this study appear to be accurate, rapid and practicable. Therefore, these techniques may be suitable for the content uniformity tests.

Ischemic-reperfused rat skeletal muscle: the effect of vasoactive intestinal peptide (VIP) on contractile force, oxygenation and antioxidant enzyme systems.

The effect of vasoactive intestinal peptide (VIP) on the nerve-stimulated contraction, tissue oxygenation, lipid peroxidation and antioxidant enzymes activities-superoxide dismutase and catalase was investigated in the rat gastrocnemius muscle exposed to 4 h ischemia-4hr reperfusion. Ischemia caused significant decrease in muscle contractile force, oxygenation and superoxide dismutase enzyme activity. Reperfusion of ischemic muscle increased the muscle contractile force and restored the tissue oxygenation to the baseline level. Superoxide dismutase and catalase activities of reperfused muscle increased significantly. However neither ischemia nor reperfusion affected gastrocnemius muscle malondialdehide (MDA) levels. VIP administration at the onset of reperfusion significantly increased skeletal muscle contractile force and tissue oxygenation even higher than baseline and reperfusion values. VIP also normalized the increased superoxide dismutase and catalase activities of reperfused skeletal muscle. In conclusion, VIP, acting as a powerful antioxidant and preserving contractile machinery seems to be a promising endogenous peptide that can salvage the skeletal muscle from severe ischemia-reperfusion injury.