Göksel Altiokka

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.

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.

Determination of amlodipine in pharmaceutical formulations by differential-pulse voltammetry with a glassy carbon electrode

A differential‐pulse voltammetric method was developed for the determination of amlodipine based on the oxidation of the dihydropyridine group on the surface of glassy carbon electrode under stationary and rotating conditions. The experiments were conducted in a supporting electrolyte consisting of 0.2 MKCl, 0.1 Mphosphate buffer, and 10 % (v/v) methanol during investigation of initial potential and pH effects. No adsorption effect was observed on using an initial potential of 0 mVand the supporting electrolyte solution at pH 5.5 under both stationary and rotating conditions. The factor affecting the voltammetric current was diffusional in the range of 200—1000 rpm for rotating, and 2—40 mV s−1 for stationary conditions up to a concentration of 0.04 mg mL−1 amlodipine. The limit of detection (LOD) and the limit of quantitative (LOQ) for the rotating and stationary techniques were found to be 0.004 and 0.0072 mg mL−1 (for S/N = 3.3) and LOQ 0.012 and 0.022 mg mL−1 (for S/N = 10), respectively. The proposed method was applied to the tablets containing amlodipine and according to the statistical evaluations acceptable results were obtained at the 95 % probability level.

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.

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.

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.

Validation of a Reversed‐Phase HPLC Method for the Analysis of Sildenafil Citrate in Pharmaceutical Preparations and in Spiked Human Plasma

Abstract A simple, precise, rapid, and accurate reversed‐phase high performance liquid chromatographic (RP‐HPLC) method has been developed for the determination of sildenafil citrate (SLD) in pharmaceutical dosage forms and spiked human plasma. Chromatography was carried out on a C18 reversed‐phase column, using a mixture of acetonitrile:water(45:55, v/v) as a mobile phase at a flow rate of 1 mL · min−1. Phenobarbital sodium was used as an internal standard (IS) and detected using a diode array detector at 220 nm. Retention times of SLD and IS were 7.2 and 3.2 min, respectively. The linear range of SLD was found to be 5×10−8–1×10−5 mol · L−1. Limit of quantitation (LOQ) and limit of detection (LOD) were calculated to be 7.5×10−8 and 2.2×10−8 mol · L−1, respectively. The method was validated for its linearity, precision, accuracy, stability, robustness, and ruggedness. The proposed method was applied to sildenafil tablets and spiked human plasma. In addition, the results were compared with those obtained from UV‐spectrophotometry.

Determination of Ticlopidine in Pharmaceutical Tablets by Flow Injection Analysis Using UV-Detection

Abstract A precise and accurate flow injection analysis method for the quantification of ticlopidine in pharmaceuticals is described. An aqueous carrier stream, which was entirely prepared with water was chosen for the flow injection analysis. The method development was achieved by using a reference standard solution of ticlopidine at 3.19 × 10−6 M concentration, which was prepared in water. The solution was injected into the instrumental system at a flow rate of 1.0 mL·min−1 and signals were detected by a UV detector at 214.2 nm. The calibration curves of TP were linear in the concentration range of 1.59 × 10−6 − 7.99 × 10−5 M. The intra- and inter-assay precision was less than 1.3% relative standard deviation. The method exhibited good linearity with the correlation coefficients close to unity. The limit of detection and limit of quantization concentrations were found to be 8.91 × 10−8 and 2.70 × 10−7 M, respectively. The effects of the tablet excipients were insignificant at the 95% probability level. The calculated tablet contents were around 99%, which is in agreement with the ranges stated by pharmacopoeias.

Rapid HPLC and Direct Flow Injection Analysis Assay for the Determination of Trimetazidine HCl in Pharmaceutical Tablet Formulation

Abstract A simple and sensitive high performance liquid chromatographic method (HPLC) and direct flow injection analysis method (FIA) are described for the determination of trimetazidine HCl (TMZ) in tablets. A mobile phase consisting of methanol:0.02 mol · L−1 potassium dihydrogen phosphate:0.005 mol · L−1 sodium dihydrogen phosphate (62:5:33 v/v/v) was used for the resolution of the compound on a reversed phase column for HPLC. For the FIA method; the best solvent system was found to be consisting of methanol:water (10:90 v/v). A flow rate of l.2 mL · min−1 was pumped and active material was detected at 210 nm. Limit of detection (LOD) and limit of quantitation (LOQ) values were found to be 1.2×10−7 mol · L−1 and 3.5×10−7 mol · L−1, respectively, for HPLC. LOD and LOQ values were found to be 2.35×10−7 mol · L−1 and 7.04×10−7 mol · L−1, respectively for FIA. The results obtained from the analysis of TMZ tablet formulations were comparable using both methods.

Determination of Azapropazone in its Pharmaceutical Form by HPLC and Flow Injection Analysis

Abstract Azapropazone is an analgesic and anti‐inflammatory agent that is used in the treatment of musculoskeletal and joint disorders, as well as in acute gout, because of its uricosuric properties. A simple and sensitive high performance liquid chromatographic method (HPLC), for the determination of azapropazone in its pharmaceutical form has been developed and validated. Azapropazone and indapamide (internal standard) were separated by a reversed phase column (Supelco Hypersil 5 µm, 150×4.6 mm ID, C18) with a mobile phase consisting of K2HPO4 (0.1 M) and methanol (55∶45, v/v) (at pH 7.0). The mobile phase was pumped at 1.2 mL min−1 flow rate then azapropazone was determined by ultraviolet detection at 251 nm. The method has an average analysis time of 5.81 min. for azapropazone. The flow injection analysis (FIA) was performed by using a carrier stream of ethanol∶water (10∶90, v/v) with a flow rate of 1.2 mL min−1. The LOD and LOQ concentrations of azapropazone for the two methods were 2.77×10−8 M and 8.41×10−8 M for HPLC, 3.65×10−7 M and 1.10×10−6 M for FIA, respectively. The results obtained from the analysis of capsule samples using both methods were compared by common statistical tests. There was no significant difference observed between the methods.