Celso Figueiredo Bittencourt

LC determination of enrofloxacin

A simple, rapid and sensitive high-performance liquid chromatographic (HPLC) method was developed for the assay of enrofloxacin in raw material and injection. The validation method yielded good results and included the range, linearity, precision, accuracy, specificity, recovery, limit of detection (LOD) and limit quantification (LOQ) values. The HPLC separation was carried out by reversed phase chromatography on a C-18 absorbosphere column (150 x 4.6 mm i.d. 5 microm particle size) with a phase composed of sodium acetate (pH 4.7; 0.1 M): acetonitrile (60:40, v/v; pH 5.0), pumped isocratically at a flow rate of 1.5 ml min(-1). The effluent was monitored at 278 nm with the eluting solvent. The calibration graph for enrofloxacin was linear from 10.0 to 80.0 microg ml(-1).

Determination of antimony(III) and total antimony by hydride generation atomic absorption spectrometry in samples of injectable drugs used for leishmaniasis treatment

A procedure for the determination of Sb(III) and total Sb in commercial samples of injectable drugs based on pentavalent antimony was proposed. The drugs studied in this work are currently used for leishmaniasis treatment in many countries. Determination of Sb was performed by hydride generation atomic absorption spectrometry under controlled conditions for the reaction medium. The following parameters were investigated: type and concentration of acid, sodium tetrahydroborate concentration and purge time. The chosen conditions for Sb(III) were: 4% (m/v) citric acid, 1% (m/v) sodium tetrahydroborate and 10 s (a pre-reduction step was performed using 10% m/v KI in 0.2% m/v ascorbic acid solution). The same parameters for total Sb determination were: 0.5 mol l−1 sulfuric acid, 4% (m/v) sodium tetrahydroborate and 10 s. Interference from As, Ni, Cu and Pb on the analytical signal for Sb(III) was also investigated. Two kinds of commercial drugs were analyzed. The trivalent Sb concentration varied from 1.7 to 3.1 mg l−1, corresponding to 1.6 to 2.8% for the total Sb. Recovery tests for Sb(III) showed values varying from 98.9 to 101.9%. The characteristic mass for Sb(III) was 0.22 ng and the detection limit (3s) was about 1.5 ng (absolute). The main advantage of the proposed procedure is to allow the determination of Sb(III) in the presence of a large excess of pentavalent Sb (about 2000 ng).

Determination of total arsenic by batch hydride generation atomic absorption spectrometry in injectable drugs containing high levels of Sb(V) as N-methylglucamine antimonate

Abstract A procedure for the determination of arsenic by batch hydride generation atomic absorption spectrometry (HG AAS) in commercial samples of injectable drugs, containing high concentrations of Sb(V), is described. The procedure is based on the complexing effect for Sb of citric, oxalic and acetic acids as reaction media. Aqua regia was used for sample digestion prior to As determination by HG AAS. The following experimental conditions for the determination of total As, as As(V), were evaluated: the acid medium and its concentration, sodium tetrahydroborate concentration, purge time, and influence of the different oxidation states of As. The effect of the delay time after mixing of sample and acid solution was also studied. Optimized conditions were: 10% (m/v) citric acid, 1.5% (m/v) sodium tetrahydroborate solution and 30 s for purge time. A delay time of 1 h was required after the digested sample had been mixed with citric acid, before As determination could be carried out. No interference on As(III) and As(V) signals was observed in the presence of up to 1 mg Sb(V). The tolerance limits for Ni(II), Cu(II) and Pb(II) were 1 mg, 100 μg and 100 μg, respectively. Recovery tests for As(III) and As(V) resulted in values between 97 and 101%. Characteristic mass and detection limit (3σ), using the recommended conditions, were 0.52 and 0.8 ng, respectively, for total As.

LC method for the analysis of cefetamet pivoxil hydrochloride in drug substance and powder for oral suspension.

A high-performance liquid chromatography isocratic procedure was developed for the assay of cefetamet pivoxil hydrochloride in drug substance and powder for oral suspension. The method validation yielded good results and included the range, linearity, precision intra- inter-day, accuracy, specificity, LOD and LOQ values. The chromatographic system consisted of a C(18) absorbosphere column (150 x 4.6 mm i.d., 5 microm particle size), a mobile phase composed of water-acetonitrile-methanol-phosphate buffer, pH 3.5 (50:35:10:5, v/v), flow rate of 1.5 ml min(-1) and UV detection at 254 nm. The relative standard deviation varied between 0.03 and 1.76%, and accuracy of 100.09% was found. Calibration curve was linear from 30.0-80.0 microg ml(-1); its correlation coefficient was 0.99989.