Voltammertric Behaviour of Clonixin and its Differential Pulse Polarographic Determination in Tablets

ABSTRACT

Clonixin, a non-steroid analgesic, can be both reduced at the mercury electrode and oxidised at the glassy carbon electrode. The anodic response shows well-defined waves in a pH range between pH 2-12. The polarographic response shows two irreversible waves or peaks in the range between pH 1-6 shifting cathodically when pH increases. Above pH 7.0 all the signals disappeared. The first signal in the dpp mode at pH 1.8 was selected for analytical use. The polarographic     

The Determination of Nitrite and Nitrate Ions by Differential Pulse Polarography

Abstract

A previously reported method for the determination of nitrite ion has been extended to include nitrate ion. Nitrate is reduced to nitrite by a cadmium column and the nitrite ion determined as diphenylnitrosamine. Cadmium interference is removed by pH adjustment and the use of KDTA.     

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%.     

Biamperometric and Differential Pulse Polarographic Methods for the Assay of Nomifensine Maleate

Abstract

Biamperometric titration and differential pulse polarography (DPP) are described for the analysis of nomifensine maleate powder and commercial capsules (Merital^R -50 mg). The biamperometric method involved the titration in cold dil. HCl medium against 0.01 M - NaN0₂ and electrometric detection of end point. The mean percent recoveries obtained were 100.0 ± 0.87 and 99.2 ± 0.95 for the authentic powder and capsules, respectively. The DPP method was performed by measuring the peak current, i_P, obtained from the recorded differential polarogram under constant 50mV modulation amplitude. The peak current was measured at the peak potential of ? 1.02 V on the dropping mercury electrode (DME) versus Ag/AgCl/KCl (sat.) reference electrode at pH 5.0 (acetate buffer). A linear relationship between peak current and concentration was demonstrated in the range 3 to 30μg ml^?1. The mean percent recovery for the capsules was 103.1 ± 1.26.     

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 Benzoylmetronidazole in Suspension Formulations by Differential Pulse Polarography

Abstract

A rapid, reproducible and accurate method for the determination of benzoylmetronidazole in pharmaceutical suspensions is presented. Differential pulse polarography at a static mercury drop electrode is used for the reduction of the nitro group of benzoylmetronidazole.     

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.     

一阶导数差示脉冲极谱法用于扑热息痛的定量分析

一阶导数差示脉冲极谱法用于扑热息痛及其制剂的定量分析，在乙醇－水－２．０×１０＾－＾３ｍｏｌ／ＬＨ２ＳＯ４（１２．５：１１．５：１）的溶液中，于０．２４Ｖ（ｕｓＡｇ／ＡｇＣｌ）处出现良好的一阶导数差示脉冲极谱峰，在３．３×１０＾－＾４～３．３×１０＾－＾３ｍｏｌ／Ｌ范围内，浓度与其一阶导数差示脉冲极谱峰值呈线性关系，检测限为７．８×１０＾－＾８ｍｏｌ／Ｌ。方法简便，快速，灵敏，结果准确。     

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.     

Determination of Codeine,Dionin and Thebaine by Differential Pulse Polarography

Abstract

The method proposed for determining codeine, dionin and thebaine by differential pulse polarography is based on the reduction (in ammoniacal medium) of the nitroderivatives obtained by dissolving the substances in concentrated nitric acid. The values of the reduction potentials range between -0.45 and -0.69 V. Morphine and heroine do not interfere in the determination of the mentioned alkaloids.     

Determination of Entacapone by Differential Pulse Polarography in Pharmaceutical Formulation

Abstract

The electrochemical methods, sampled direct current, and differential pulse polarography, were developed successfully and applied to the routine determination of Entacapone in pharmaceutical formulation. Both methods gave rise to three reduction waves or peaks respectively. The irreversibility and the diffusion‐controlled of the first reduction were confirmed by cyclic voltammetry. The limiting currents are directly proportional to the concentration of entacapone with a correlation coefficient of 0.99. The within‐day coefficients of variation and the day‐to‐day coefficient of variation were less than 3.5% for entacapone and Comtan^®. The percentage recovery for entacapone in tablets is satisfactory for both methods. The method is simple without any pretreatment.     

定量测定秦皮中秦皮甲素的二阶导数示差脉冲极谱法

建立了中草药秦皮中秦皮甲素的二阶导数示差脉冲极谱定量分析方法。秦皮甲素在乙醇－2mol/L氯化锂－水（体积比2：1：5）的底液中,于－1．703V（vs Ag/AgCl)处出现一良好的二阶导数示差脉冲极谱峰,其峰幅值与秦皮甲素在0．2－1．6mmol/L范围内呈非常显著的线性关系（P＜0．01）,检测下限脒50mmol/L。该法简便、快速、灵敏,结果准确。     

两种蒙药中锗的差示脉冲极谱测定及其红外光谱的差异

采用差示脉冲极谱法,以3,4-二羟基苯甲醛的0.072 mol·L-1硫酸溶液作为底液,在峰电位为-0.53 Ⅴ(vs．Ag/AgCl),锗(Ⅳ)浓度在1.03×10-5～1004×10-4mol·L-1范围内与峰电流呈线性关系.据此测定了阿嘎日-35和阿嘎日-8中总锗、无机锗、有机锗含量,并利用红外光谱比较了两种蒙药的红外谱图的差异,据此可对两种蒙药予以区别.     

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.     

Indirect Determination of Trace Tetraborate by Differential Pulse Polarography Using Its Copper Complex and Application to Waste and Drinking Water

A new differential pulse polarographic (DPP) method has been developed for the trace determination of boron. Its most stable copper complex is used in 0.5 M KNO₃ electrolyte since boron is not electroactive. By continuous addition of tetraborate to copper solution, the copper peak decreased first but then the peak became very small and nearly constant. This point was used for the boron determination. It was found that one mole of copper used two moles of tetraborate. Using this relationship, 1×10^?5 M tetraborate could be determined. The quantification limit was 2.5×10^?6 M and detection limit was 8×10^?7 M. In the presence of complex forming ions such as Pb, Zn, and Cd, the borate found in sample was somewhat smaller because of their reaction with borate. But since their complexes were not as strong as copper, only a few percent of borate were used. No interference was observed in the presence of calcium, chloride and sulfate. This method is applied for the determination of B in borax ore, waste water of borax industries and tap water of Ankara city.     

微分脉冲溶出伏安法测定2,4-二硝基-1-萘酚

以Britton-Robinson(pH=8.0)缓冲液为底液,富集电位为-0.05V,富集时间为30s,电位扫描速率20mV/s,产生2个完全分离的峰,在-0.58±0.01V(vs.Ag/AgCl)处产生的峰灵敏度高且峰形好,故以此峰为定量峰。2,4_二硝基_1_萘酚浓度在6.00×10-8～2.00×10-6mol/L时与峰电流呈良好的线性关系,线性相关系数为0.9996。检出限为4.00×10-9mol/L,信噪比S/N约为10。     

Sensitive Differential Pulse Polarographic Determination of Molybdenum Using The New Catalytic System Mo(VI)‐Phenantroline‐Chlorate

It was found that in acidic chloride media the complex of Mo(VI) with 1,10‐phenantroline induces catalytic reduction of KClO₃. This catalytic effect can be utilized for sensitive differential pulse polarographic determination of Mo(VI) with a low detection limit of 2.9×10^?11 M (2.8 ng/L). The optimal Mo(VI) response was obtained at pH 2.8, in the presence of (6–12)×10^?5 M 1,10‐phenantroline and 2×10^?2 M KClO₃. The sensitivity was 1.73 nA/nM and the catalytic response was linear up to 7.5×10^?7 M Mo (VI). The interferences from inorganic ions and surface‐active substances were investigated. The results of the determination of Mo(VI) in CRM water sample showed good reproducibility (R.S.D. for standard solution is below 1.2% and for water samples is 8.9%) and accuracy of the elaborated catalytic polarographic method.     

Simultaneous Trace Determination of Nickel and Cobalt in Natural Waters by Differential Pulse Polarography

Abstract

A differential pulse polarographic method has been developed for the simultaneous low level determination of nickel and cobalt in the presence of furildioxime in natural waters. The nature of the electrode processes was studied with cyclic voltammetry. Limits of determination of 0.4 μg/L and 0.15 μg/L were achieved for nickel and cobalt respectively     

Differential Pulse Polarographic Determination of Trace Molybdenum in Uranium with α-Benzoinoxime Extraction

A method for the determination of trace molybdenum in uranium is described based on its specific catalytic reduction wave in the presence of nitric acid. Molybdenum is separated from uranium by α-benzoin oxime extraction and determined by differential pulse polarography. As lower as 1 ng/ml of Mo(VI) is determinable and 98% of recovery can be obtained at present work.