Enoxacin: Polarographic Behaviour and Its Determination in Pharmaceutical Forms

Abstract

A differential pulse polarographic method for the identification and quantitative determination of enoxacin is described. The method is based on the electrochemical reduction of the drug at the dropping mercury electrode. It gives a well-developed polarographic response with a half-wave potential of -990 mV vs. SCE in 0.1 M HCl. The electroactive specie exhibits a diffusion-controlled polarographic wave and its limiting current shows a linear dependence with the enoxacin concentration in the range between 5.10^?4 mM and 1 mM. This characteristic is applied for determination of enoxacin in commercial tablets. The recovery study shows a good accuracy and precision for the developed assay (average of 101.1% and standard deviation of 1.99). Furthermore, a comparative UV spectrophotometric assay also is developed.     

Differential-pulse polarographic determination of the insecticide imidacloprid in commercial formulations

The reduction reaction of imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] at a mercury electrode shows two well-defined waves in the range of pH 2.0–11.0. The characteristics of the electrode processes were examined. The analyte captures four electrons in the first step and two in the second to give the hydroxylamine and amine derivatives, respectively. A differential-pulse polarographic method for the determination of imidacloprid based on the first reduction peak of this compound is presented. Britton-Robinson buffer was used as a supporting electrolyte and optimum pH value was found to be pH 8.O. The applicable concentration range was from 10 to 200 ng/ml, with a relative standard deviation of 1.5% (for a level of 80 ng/ml) and a detection limit of 3 ng/ml. The method has been satisfactorily applied to the determination of imidacloprid in commercial formulations.     

Rapid Differential Pulse Polarographic Determination of Thiamethoxam in Commercial Formulations and some Real Samples

The polarographic behavior of thiamethoxam (a neonicotinoid insecticide) was studied by direct current and differential pulse polarography. Depending on the pH thiamethoxam exhibited one or two well-defined cathodic polarographic waves. The characteristics of the electrode reaction were investigated and it was found that at pH > 5.0 the target molecule captures four electrons in the first step, and two in the second. Based on the reduction behavior of the target molecule on the mercury electrode, a differential pulse polarographic method was elaborated for the rapid determination of thiamethoxam at pH 8.0. With the optimized method, a linear response for thiamethoxam was found in the concentration range of 31.1 − 470 ng cm⁻³, the relative standard deviation did not exceed 1.6%, and the detection and quantitation limits were found to be 9.3 ng cm⁻³ and 31.1 ng cm⁻³, respectively. The method was applied to the determination of thiamethoxam in commercial formulations and real samples (potato and maize). The procedure is simple, fast, sensitive, and compares well with comparative spectrophotometric and chromatographic (HPLC/DAD) methods.     

Polarographic behaviour and determination of paracetamol and salicylamide after treatment with nitrous acid

A polarographic procedure is described for the determination of paracetamol (acetaminophen) and salicylamide after treatment with nitrous acid. The different experimental parameters affecting the derivatization process and the polarographic analysis were studied. The derivatization products were found to be reduced at the dropping mercury electrode over the whole pH range in Britton-Robinson buffers. At pH 7.0, well defined diffusion-controlled cathodic waves were produced for both compounds. Plots of limiting current vs. concentration were linear over the ranges 0.05–0.75 and 0.25–1.5mM for paracetamol and salicylamide, respectively, in the d.c. mode, with minimum detectability of 2.5 × 10^–6 and 1.25 × 10^–5 M, respectively. The procedure was applied to the analysis of some pharmaceutical dosage forms and the results were in good agreement with those obtained by official and compendial methods.     

Simultaneous Polarographic Determination of Lead (II) and TIN (II) by Multivariate Calibration

ABSTRACT

The polarographic waves of lead (II) and tin (II) overlap due to their similar reductive potentials and it is difficult to determine these two components simultaneously without a pre-separation. In this paper, differential pulse polarography (DPP) combined with multivariate calibration approaches, such as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS), were successfully applied to the resolution of overlapping polarographic waves of these two components in the concentration range of 0.05-3.50 mg 1^?1. Satisfactory quantitative results were obtained.     

Polarographic Determination of Aztreonam

Abstract

The polarographic behaviour of Aztreonam is studied. In acid media, at pH values lower than 6, in differential pulse polarography a peak is observed at a potential close to ? 0.6 volts. The optimum conditions for the polarographic signal are established and the different parameters affecting the electrochemical process are studied. The relationship between peak intensity and the concentration of Aztreonam is linear for concentrations lower than 1.0 ? 10^?5 M, the detection limit being 1.4 × 10^?8 M It was observed that the presence of 1-arginine does not affect the polarographic signal of Aztreonam to any significant extent.     

Electroanalytical Study of the Reduction of Sb(III) in Tartrate Medium

Abstract

A systematic study on the reduction of Sb(III) on a mercury electrode in aqueous solution of tartrate ion has been carried out. The nature of the electrode reactions has shown to be a function of the acidity of the solution. Results from polarographic, coulometric and voltammetric experiments allow us to outline a model of electrode reaction according to which different Sb-tartrate complex ions can be reduced. Sensitivity and detection limits for the polarographic determination of Sb(III) in tartrate medium are given using several polarographic waves obtained at different pH. In this way, the selection of the basic medium is vindicated.     

Differential Pulse Polarographic Determination of Orthophosphate in Nonaqueous Media

Abstract

The method is based on the polarographic behavior of 12-tungstophosphoric acid in nonaqueous media at the DME utilizing the differential pulse polarographic technique. In this procedure, orthophosphate is converted to 12-tungstophosphoric acid H₃ PW ₁₂ O ₄₀ by reacting with tungstate under acidic conditions and at 100°C. The H₃ PW ₁₂ O ₄₀ is extracted into 1-pentanol and its polarographic measurement is made in 1-pentanol-ethanoi mixture containing sodium perchlorate as supporting electrolyte. The differential pulse polarogram of H₃ PW ₁₂ O ₄₀ in this solution shows three peaks between 0.00 and -0.90 V vs. Ag/ AgCl. The most cathodic peak at -0.78 V exhibited the highest peak current value and was used for the analytical measurement. A linear calibration graph in the range 0.10 - 5.00 pg/ml P in the final solution was obtained. The method has a relative standard deviation of 0.90% at the 4 pg/ml P level and 1.32% at the 1 μg/ml P level in the final solution. Arsenate, borate and silicate do not interfere.     

Determination of Nitrite by Single-Sweep Polarography

Abstract

A new method for determining nitrite is proposed. the mechanism for the polarographic waves and the condition for determining nitrite are discussed in this paper. In cathodic sweeps, the peak height is directly proportional to the concentration of nitrite over the range 5×10^?9?6×10^?7 g/ml, the detection limit is 4×10^?9g/ml. the experiments showed that this polarographic wave is an adsorption wave, and useful in determination of nitrite in water sample.     

Polarographic Behaviour of Trazodone

Abstract

Trazodone, which cannot be electrochemically reduced at the dropping mercury electrode, exhibits catalytic proton reduction waves as shown by the strong modifications occuring with variations of pH, concentration, nature of the buffer, ionic strength and presence of organic solvent. The catalytic process is developing three successive waves with rising pH or concentration, depending on the protonation rate or the adsorbed state. The influence of sodium ions indicates a decrease of sorbtivity with the proton concentration. The strong surface character of the wave observed in very acidic media decreases gradually on behalf of a more pronounced bulk character with increasing pH. The wave recorded in neutral media is of analytical interest, a linear calibration curve being plotted in the 2.10^?6 M to 1.10^?3 M concentration range.     

Differential Pulse Polarographic Determination of Moxifloxacin Hydrochloride in Pharmaceuticals and Biological Fluids

Abstract

A simple, fast, sensitive and fully validated differential pulse polarographic (DPP) method for the determination of trace amounts of moxifloxacin in pharmaceutics, serum and urine is reported. Moxifloxacin exhibited irreversible cathodic peak over the pH 5.00–11.00 in Britton–Robinson (B–R) buffer. At pH 10.00 (the analytical pH), a well‐defined peak at ?1.61 V versus saturated calomel electrode was obtained. The current has been characterized as being diffusion‐controlled process. The diffusion current constant (i_d) was 1.48±0.12 and the current–concentration plot was rectilinear over the range from 5×10^?7 to 1×10^?4 M with correlation coefficient (n=10) of 0.995.

The proposed method was applied to commercial tablets and average percentage recovery was in agreement with that obtained by spectrophotometric comparison method. The method was extended to the in vitro determination of moxifloxacin in spiked human serum and urine.     

Estimation of tungstate ion by tensammetry

It is shown that tungstate ion can be estimated quantitatively by the same experimental technique as that used for alternating current polarography. The underlying process differs, however, fundamentally from polarography in that no electron transfer takes place at the electrode and thus no d.c. polarographic steps arc obtained. The alternating current is produced solely by adsorption/ desorption processes at the electrode/solution interface, a phenomenon to which the name “tensammetry” has been given.The current-voltage curve for sodium tungstatc at pH 1.8 shows two -well defined tensammetric waves which can be used for purposes of quantitative estimation. No waves are obtained at pH values higher than 6, showing that the compound responsible for the production of the waves is not the simple WO₄^-4ion.     

The Polarographic Determination of Tenoxicam in the Pharmaceutical Preparations

Abstract

In this study, the polarographic behaviour and the optimum polarographic conditions for the determination of TNX using DC (direct current), DP (differential pulse), SCAP (superimposed constant amplitude pulse) and SIAP (superimposed increasing amplitude pulse) polarographic techniques are described based on the reduction of enol group of the molecule on the dropping mercury electrode. The experiments were conducted in the aqueous supporting electrolyte solution containing 0.2 M KCl and 0.2 M buffer solution. Single waves were obtained at various pH values. The limiting currents were decreased and E_1/2 values were linearly shifted to more negative potentials with an increase in the pH. The system was irreversible at both the acidic and the basic media and it was adsorptional in the acidic medium and diffusional at pH 10.8. The variation in the limiting current was found to be 0.86 μA/°C. Good relations were obtained for DC, DP, SCAP and SIAP polarographic techniques at pH 10.8. The determination of TNX in pharmaceutical preparations, namely Tilcotil® tablets, containing 20 mg of TNX were tested employing DC, DP, SCAP, SIAP polarographic techniques. The results were compared to those of HPLC and the standard deviations (SD) were found to be in the range of 0.14 and 0.22 for the techniques employed for filtered and unfiltered solutions. The polarographic techniques used for the determination of TNX seem to be accurate, rapid and practical. Therefore, the suggested method may be promising in the routine analysis.

     

Differential Pulse Polarographic Determination of Some (5-Nitro-2-Furl)Alkylidene-2-Hydrazinothiazole Derivatives

Abstract

The differential pulse polarographic analysis of four (5-nitro-2-furyl)alkylidene-2-hydrazinothiazole derivatives are presented, 0.1 M tetramethylammonium tetrafluoroborate solution was found to be the best supporting electrolyte. At static mercury drop electrode the nitro group of the compounds studied was reduced to the amine in a six-electron process. Linear response was observed over 0.2 to 140 mg.L^?1 with a relative standard deviation of 3.3%.     

辛可尼丁的催化氢波

在浓度为０．２ｍｏｌ／Ｌ ＮＨ３·Ｈ２Ｏ－０．２ｍｏｌ／Ｌ ＮＨ４Ｃｌ（ｐＨ＝９．２０）的底液中,辛可尼丁在单扫示波极谱上有一灵敏的催化氢波。导数波峰电位于－１．４２Ｖ（ｖｓ,ＳＣＥ）附近。该峰具有一定吸附性。     

Electrochemical determination of hydrogen peroxide using o -dianisidine as substrate and hemoglobin as catalyst

A new electrochemical method for the determination of microamounts of hydrogen peroxide utilizing o-dianisidine (ODA) as substrate and hemoglobin (Hb) as catalyst is described in this paper. Hb can be used as mimetic peroxidase and it can catalyse the reduction of hydrogen peroxide with the subsequent oxidation of ODA. The oxidative reaction product is an azo compound, which is an electroactive substance and has a sensitive second-order derivative polarographic reductive peak at the potential of -0.58 V (vs. SCE) in pH 80 Britton-Robinson (B-R) buffer solution. The conditions of Hb-catalytic reaction and polarographic detection of the reaction product were carefully studied. By using this polarographic peak and under optimal conditions, the calibration curve for the H₂O₂ was constructed in the linear range of 2.0 x 10^-7 ∼ 10 x 10^-4 mol/l with the detection limit of 5.0 x 10^-8 mol/l. This method can also be used to the determination of Hb content in the range of 20 x 10^-9 ∼ 30 x 10^-7 mol/l with a detection limit of 10 x 10^-9 mol/l. The proposed method was further applied to the determination of the content of H₂O₂ in fresh rainwater with satisfactory results. The catalytic reaction mechanism and the electrode reductive process of the reaction product were carefully studied.     

Differential Pulse and Cathodic Stripping Voltammetric Methods for the Determination of Aromatic Sulfones

Abstract

A cathodic stripping voltammetric method for the determination of aromatic sulfones was developed. The technique involved a conversion of the sulfone to a sulfinate by controlled potential electrolysis at a mercury pool electrode and a subsequent determination of the sulfinate by cathodic stripping at a silver electrode. The detection limit was 2 × 10^?7 M sulfone in 4:1 DMSO-H₂O.

The differential pulse polarographic method utilized direct reduction of the sulfone in a 3:2 DMSO-benzene solvent. Although the detection limit (4.6 × 10^?7 M) was higher than in the stripping method, the linear dynamic range was greater (500 vs. 25), the typical precision was better (0.5 v. 7% relative standard deviation) and the determinations were more rapid (20 vs. 90 min). In addition, fewer interferences are anticipated for the pulse polarography method.     

Anodic Polarographic Behaviour of Hydrolyzed Penicillin V

Abstract

The electroactivity of a degradation product from penicillin V is described. This electroactive product is formed by acidic hydrolysis at pH 4.0 and heating at 90°C for 60 minutes.

This derivative has not been identified, but would seem to contain a thiol group. It gives a diffusion controlled anodic polarographic wave with a peak potential of -0.204 V versus SCE at pH 4.0.

The developed method has been applied to the analysis of penicillin V dosage forms and a recovery of 100.8 has been obtained.     

Differential-pulse polarography of amino acids in acetaldehyde-borax medium

A differential-pulse polarographic method for the determination of amino acids is reported, based on the formation of Schiff's base compounds in borax buffer solution (pH 10.10) containing acetaldehyde. The compounds are reduced at a mercury electrode with peak potentials of about ?1.5 V (vs. SCE) and well defined polarographic waves are obtained which can be used to determine amino acids in borax medium. The differential-pulse polarographic method was found to be the most sensitive and suitable for the determination of amino acids in the concentration range 1 × 10^?6–8 × 10^?4 M (lysine) and 2.8 × 10^?6–1 × 10^?3 M (arginine). The polarographic characteristics of these waves were studied by differential-pulse polarographic and cyclic voltammetric methods. The waves are ascribed to the reduction of the imido group in the Schiff's base compounds. The procedure was applied to the determination of lysine and arginine in foodstuffs and the total proteins in serum samples.     

Polarographic behaviour of salicylaldehyde-2-pyridylhydrazone and its copper(II) complex

The polarographic behaviour of salicylaldehyde-2-pyridylhydrazone (SAPH) has been studied in aqueous buffer solution containing 40% ethanol using DC and DP polarographic methods. In the pH range 1.8–7.5 the observed single irreversible reduction wave is assigned to the splitting of the N-N bond and reduction of C=N centre. In alkaline medium, a second wave appears at a more negative potential due to the reduction of the salicylaldehyde which is formed by hydrolytic decomposition of the SAPH molecule. The effect of pH on the limiting current andE _1/2 as well as the reduction mechanism are discussed and compared with similar compounds. The kinetic parameters of the electrode reaction have been calculated.The analytical properties of the copper(II)-SAPH system is described. The complex gave rise to a single irreversible well-defined wave (E _1/2=–0.58 V at pH=5.2). The reaction process is diffusion controlled. A method is suggested for the determination of Cu(II) in presence of different metal ions as the difference in theirE _1/2 values is sufficient for the purpose.This work is taken partly from the M. Sc. Thesis of Jamal S. Shalabi