Determination of Some Phenothiazines Compounds in Pharmaceuticals and Human Body Fluid by Electrocatalytic Oxidation at a Glassy Carbon Electrode Using Methylene Blue as a Mediator

Abstract

A glassy carbon electrode plus Methylene blue as a mediator was employed to study and sense the electrocatalytic oxidation of phenothiazines, including chlorpromazine, perphenazine, promazine, and fluphenazine, using cyclic voltammetry and chronoamperometry as diagnostic techniques. The electron-transfer coefficient, alpha (= 0.45), for phenothiazines compounds at the surface of glassy carbon electrode was determined using a cyclic voltammetry technique. It was found that under a selected pH (8.6) the peak current due to the oxidation of Methylene blue at the surface of the electrode that occurrs at a potential of about ? 180 mV is proportional to the phenothiazines concentration. Linear analytical curves were obtained in the ranges of 1.0 × 10^?6 ? 2.1 × 10^?4 mol L^?1 for the phenothiazines compounds. The influences of potentially interfering substances on the current response of the system were examined. The method was used for the determination of phenothiazines compounds, including chlorpromazine, perphenazine, promazine, and fluphenazine in human.     

Individual and Simultaneous Stopped-Flow Fluorimetric Determination of Perphenazine and Chlorpromazine

Abstract

The stopped-flow technique is used to develop fluorimetric determinative methods for two phenothiazine drugs: perphenazine and chlorpromazine. The methods are based on the oxidation of these compounds to their corresponding fluorescent sulfoxides. Owing to the intrinsic characteristics of this technique, which allow rapid and thorough mixing of reactants, the oxidation is affected by dissolved oxygen itself, which therefore makes an oxidizing reagent unnecessary. Two methods are proposed for each phenothiazine, one based on initial rate and another on maximum fluorescence intensity measurements. Their linear ranges are 0.1–40 μg mL^?1 and their precision (%RSD) between 0.9 and 2.8%. These methods have been satisfactorily applied to the determination of both phenothiazines in several pharmaceutical preparations. On the basis of the additivity of the initial rate and maximum fluorescence intensity of perphenazine and chlorpromazine, the proportional equations principle is applied to the simultaneous determination of these compounds. Perphenazine/chlorpromazine mixtures in ratios between 1:8 and 8:1 are successfully resolved.     

Spectrophotometric Determination of Bromate in Water Using Multisyringe Flow Injection Analysis

A multisyringe flow injection system for the spectrophotometric determination of bromate in water is proposed, based on the oxidation of phenothiazine compounds by bromate in acidic medium. Several phenothiazines were tested, including chlorpromazine, trifluoperazine, and thioridazine. Higher sensitivity and lower LOD were attained for chlorpromazine. Interference from nitrite, hypochlorite, and chlorite was eliminated in-line, without any changes in the manifold. The automatic methodology using chlorpromazine allowed the determination of bromate between 25 and 750 µg L^?1, with LOD of 6 µg L^?1, good precision (RSD < 1.6%, n = 10), and determination frequency of 35 h^?1.     

Indirect Catalytic Spectrophotometric Determination of Metamizol Following Oxidation by Lead Dioxide Immobilized in A Polyester Resin Bed

Abstract

A spectrophotometric-indirect procedure for the determination of metamizol is described. The method is based on the reaction of the drug in a solid-phase (lead dioxide immobilized in a polyester resin bed) in acidic media (perchloric acid 0.01 M as carrier). The lead dioxide reactor provides simultaneously an effective oxidation of the drug and a controlled liberation of Pb(II) which acts as catalyst on the reaction pyrogallol red-potassium persulphate; the oxidation of the red pyrogallol results in a less coloured solution. The decreased red colour (negative FIA peaks) is monitored at 520 nm. The calibration graph is linear in the interval 2–16 ppm in metamizol. The relative standard deviation for the determination of 10.4 ppm of metamizol is 2.9% (n=23) and the sample throughput is 72 h^?1.     

2-(2-Thiazolylazo)-p-cresol(TAC) as a Reagent for the Spectrophotometric Determination of Lead(II)

Abstract

The reaction between lead(II) and 2-(2-Thiazolylazo)-p-Cresol(TAC) in the presence of TERGITOL NPX (4 mg/ml) at an apparent pH 9.0–10.0 results in an intensely colored complex which is stable for at least 4 hr.

The composition of the complex is 1:2 cation: TAC and the log of the formation constant is 11.92 ± 0. 40. Beer's law is obeyed up to 6.0μg.ml^?1 of lead(II) at 650nm.

The apparent molar absorptivity at 650 nm is 2.07 × 10⁴ 1. mole^?1.cm^?1 and the detection limit was obtained as 10.0 ng.ml^?1 of lead(II).

The method is applied to determination of lead(II) in copper-base alloy.     

Kinetic Spectrophotometric Determination of Nanogram Levels of Manganese (II) Based on its Catalytic Effect on the Oxidation of an Azo Compound with Potassium Periodate in the Presence of 1, 10-Phenanthroline

ABSTRACT

The catalytic effect of manganese (II) on the oxidation of Diphenylamine-4-azo-benzen-4'-sulfonic acid potassium salt with potassium periodate in the presence of 1, 10-phenanthroline in weakly acidic media was studied. A catalytic kinetic spectrophotometric method for determination of manganese (II) in the range 0.05 – 2.5 ng ml-^?1 can be determined by the fixed-time method with a detection limit of 0.017 ng ml-^?1. The method was applied successfully to the determination of manganese (II) in tap water and human urine.     

Kinetic-Fluorimetric Determination of Choline and Acetylcholine by Oxidation with Ce(IV)

Abstract

A kinetic fluorimetric method for the determination of choline and acetylcholine based on the oxidation of these analytes by Ce(IV) in a sulfuric acid medium yielding fluorescent Ce(III) is proposed. The calibration graph of each analyte is linear over the range 1.7x10^?5 ? 1×10^?3 M and the relative standard deviation is about 2% in both cases. The rate of appearance of Ce(III) fluorescence was found to be influenced by various processes in addition to the oxidation reaction and experiments were carried out in order to elucidate them.     

Electroanalytical Determination of Opipramol in Pharmaceutical Preparations and Biological Fluids

Abstract

The electrooxidative behavior and determination of opipramol, a tricyclic compound for therapy of anxious-depressive states and general anxiety disorder, were investigated at a glassy carbon electrode using cyclic, linear sweep, differential pulse and Osteryoung square wave voltammetric techniques. The oxidation of opipramol was irreversible and exhibited a diffusion controlled process dependent on pH using a glassy carbon electrode. The oxidation mechanism on a glassy carbon electrode is proposed and discussed. The anodic process can be attributed to the oxidation of azepine and piperazine rings. Different parameters were tested to optimize the conditions for the determination of opipramol. The dependence of current intensities and potentials on pH, concentration, scan rate, and nature of the buffer was investigated as detailed. Opipramol in pH 3.7 acetate buffer presents a well-defined anodic response at + 0.86 V according to studies of the proposed method. The determination of opipramol was in pH 3.7 acetate buffer, which allowed quantitation over the 2 × 10^?6 to 2 × 10^?4 M range in the supporting electrolyte, 2 × 10^?6 to 6 × 10^?5 M range in the spiked serum sample, and 2 × 10^?6 to 1 × 10^?4 M range in the urine sample, for both techniques. The proposed method was applied to commercial drageés and average percente recovery was in agreement with that obtained by spectrophotometric comparison methods. The method was extended to the in vitro determination of opipramol in spiked human serum and urine.     

Determination of Chlorpromazine in Aqueous Solutions as Studied by Photoacoustic Spectroscopy Using a Carbon-Black Detector

Abstract

A simple, fast and reproducible method for determination of chlorpromazine (CLP) is presented. Calibration curves are prepared for the 6.0 mol.dm^?3 solutions of 1.0×10^?6 to 1.0×10^?4 CLP which are oxidized with equivalent volumes of standard Ce⁺⁴ solutions to a highly coloured (λmax⁼⁵²⁵ nm.) semiquinone cation radical. Conventional photometric and photoacoustic techniques using carbon-black detection (CBD) gave consistent results and are used to calculate the CLP content of tablets and ampuls with a good precision, and an overall accuracy of 1.9% and ～3% respectively.     

Square‐Wave Voltammetry Determination of Aspartame in Dietary Products Using a Boron‐Doped Diamond Electrode

Abstract

The use of square‐wave voltammetry in conjunction with a cathodically pretreated boron‐doped diamond electrode for the analytical determination of aspartame in dietary products is described. In this determination, the samples were analyzed without previous treatment in a 0.5 mol l^?1 H₂SO₄ solution. A single oxidation peak at a potential of 1.6 V vs. Ag/AgCl (3.0 mol l^?1 KCl) with the characteristics of an irreversible reaction was obtained. The analytical curve was linear in the aspartame concentration range 9.9×10^?6 to 5.2×10^?5 mol l^?1 with a detection limit of 2.3×10^?7 mol l^?1. The relative standard deviation (n=5) obtained was smaller than 0.2% for the 1.0×10^?4 mol l^?1 aspartame solution. The proposed method was applied with success to the determination of aspartame in several dietary products and the results were similar to those obtained using an HPLC method at 95% confidence level.     

Spectrophotometric Determination of Cobalt in Vitamin Preparations,Steel and Iron Using 2-Hydroxy- 1-Naphthaldehyde Guanylhydrazone

Abstract

A new spectrophotometric determination of cobalt with 2-hydroxy-1-naphthaldehyde guanylhydrazone in acid medium is described. The method is developed on the basis of a yellow cobalt (III) complex (molar absorptivity 1.32×10^?4 L.mol^?1.cm^?1 at 416 nm, stoichiometry 2:1). The method was applied to the determination of cobalt in vitamin preparations, steel and high-purity iron.     

Colorimetric Determination of Some N-Substituted Phenothiazine Derivatives Using 2-Iodoxybenzoate

Abstract

A new, sensitive colorimetric method has been described for the quantitative determination of six N-substituted phenothiazines. the method depends on the formation of stable phenothiazine free radical by the use of 2-iodoxybenzoate as chromogenic reagent. the drug in 50% sulphuric acid is treated with reagent (5×10^?4 M). the produced red or purple color possesses characteristic absorption maximum for each of the drugs tested. Beer's law is obeyed over the concentration range 2-30 μg.ml^?1 with apparent molar absorptivities ranging from 9.4-12.4×10^?3 for the studied phenothiazine derivatives. the average % recovery is 99.5±0.96 - 101.6±1.01. the method was applied successfully to the microdetermination of promazine. HCl, chlorpromazine, HCl, promethazine. HCl, perphenazine, levomepromazine HCl and mesoridazine besylate either in pure form or incorporated in their representative pharmaceutical preparations. the stoichiometry of the reaction was assumed and a reaction mechanism was suggested. the precision of the assay was comparable with the official ones.     

The Permanganate Ion in Alkaline Solutions as a Reagent for CS2N− 3Analytical Determination - A Potentiometric Method

Abstract

The oxidation of the 1, 2, 3, 4-thiatriazol-5-thiolate ion CS₂ N^? ₃by, permanganate ions in an alkaline medium was investigated. The pseudo-halide undergoes a quantitative seventeen-electron change reaction yielding sulphate, nitrogen and carbon dioxide as final products. Despite the similar chemical behavior exhibited by thiocyanate and CS₂N^? ₃ ions the experimental data strongly suggested that the oxidation reactions of the pseudo-halides dealt with in this study do not follow the same mechanism. On the basis of this reaction an oxidative analytical method was developed for the CS₂N^? ₃. The pseudo-halide is oxidized by an excess of permanganate ions. The remaining oxidant is titrated with standardized thalium (I) or hexacyanoferrate (II) solutions. Considerable improvements over former procedures were achieved employing two polarized platinum electrodes to detect the end point, by potentiometry. The method proposed here is simple, precise, accurate, rapid and allows the determination of pseudo-halide concentrations down to 1 × 10^?3 M.     

Simultaneous Voltammetric Determination of Lead and Tin by Adsorptive Differential Pulse Stripping Method and Orthogonal Signal Correction‐Partial Least Squares in Water Samples

An adsorptive differential pulse stripping method for the simultaneous determination of lead and tin is proposed. The procedure involves an adsorptive accumulation of lead and tin on a hanging mercury drop electrode (HMDE), followed by oxidation of adsorbed lead and tin by voltammetric scan using differential pulse modulation. The optimum experimental conditions are: 0.2 mol L^?1 HNO₃, accumulation potential of ?900 mV versus Ag/AgCl, accumulation time of 200 s, scan rate of 20 mV s^?1 and pulse height of 80 mV. Lead and tin peak currents were observed in the same potential region at about ?400 mV. The simultaneous determination of lead and tin by using voltammetry is a difficult problem in analytical chemistry, due to voltammogram interferences. The resolution of a mixture of lead and tin by the application of orthogonal signal correction‐partial least squares (OSC‐PLS) was performed. The linear dynamic ranges were 0.003‐0.35 and 0.008‐0.50 μg mL^?1 and detection limits were land 3 ng mL^?1 for lead and tin, respectively. The RMSEP for lead and tin with OSC and without OSC were 2.8737, 6.0557 and 8.0941, 9.5151, respectively. The capability of the method for the analysis of real samples was evaluated by the determination of lead and tin in water samples with satisfactory results.     

Modified Glassy Carbon Electrode with Multiwall Carbon Nanotubes as a Voltammetric Sensor for Determination of Leucine in Biological and Pharmaceutical Samples

Abstract

A simple and highly sensitive method is described for voltammetric determination of leucine in blood and urine samples; namely, a glassy carbon electrode with an effective method is modified with multiwall carbon nanotubes (MWNTs). The cyclic voltammetric results indicated that MWNTs remarkably enhanced electrocatalytic activity toward the oxidation of leucine. Under the optimum condition the calibration curve was linear in the concentration range 9.0 × 10^?6 ? 1.5 × 10^?3 mol L^?1, with the detection limit of 3.0 × 10^?6 mol L^?1 and a relative standard deviation (RSD%) lower than 3.0% (n = 5). Also, some kinetic parameters were determined and a multistep mechanism for oxidation of leucine was proposed.     

Automated stopped-flow system in pharmaceutical and clinical analysis : Kinetic determination of acetaminophen in formulations and serum by using the iron(II)—2,4,6-tris(2-pyridyl)-s-triazine

The development of automated stopped-flow spectrophotometric systems, their potential in automated routine determinations using kinetic and fast equilibrium techniques and several examples of applications are briefly reviewed. The use of a compact, inexpensive laboratory-made stopped-flow system for the measurement of reaction rates and a fast equilibrium method for the determination of acetaminophen in formulations and serum are described. The reaction-rate method is based on monitoring the oxidation of acetaminophen by iron(III) in the presence of the chelating agent 2,4,6-tris(2-pyridyl)-s-triazine to form a highly absorbing complex of iron(II). The calibration graph is linear in the range 20–200 μg ml^?1, with a precision of 0.8–2.6%, a detection limit of 5.5 μg ml^?1 and a measurement throughput of 120 per hour. Common excipients do not interfere and the analysis of commercial formulations gave results similar to those of a reference method. The optimization of the experimental conditions was done by a kinetic study of the reaction and some kinetic parameters are given.The method for the determination of acetaminophen in serum is based on a rapid measurement of the absorbance of the reaction mixture after a delay time of 15 s in the presence of chlorpromazine, which catalyses the reaction. Acetaminophen is isolated by extraction with ethyl acetate and the calibration graph is linear in the range 0.5–6 μg ml^?1 with a detection limit of 0.04 μg ml^?1 and a precision of 1.5%. The proposed method showed a decreased interference from drugs that also react with iron(III).     

Chemiluminescence Determination of Sulfite and Sulfur Dioxide Using Tris(1,10-Phenanthroline)Ruthenium-KMnO4 System

Abstract

The emission produced by sulfite after oxidation by potassium permanganate in acidic solution in the presence of Ru(phen)₃ ²⁺ is used to determine 1.0 × 10^?7 to 2.5 × 10^?5 mol/L sulfite. The limit of detection is 4.5 × 10^?9 mol/L and the relative standard deviation is 3.1% for a 1 × 10^?5 mol/L sulfite solution (n=8). The method was also applied satisfactorily to the determination of sulfur dioxide in air by using triethanolamine (TEA) as absorbent material.     

Dioctadecyldimethylammonium Chloride Bilayer Membrane Vesicle-Enhanced and Manganese (II)-Catalyzed Chemiluminescence for Determination of Adrenaline by a Flow-Injection Method

Abstract

A new chemiluminescence system reinforced by use of a surfactant and a metal catalyst is demonstrated for selective determination of adrenaline by a flow-injection method. The weak light emission originating from an aerobic oxidation of adrenaline in an alkaline solution is dramatically enhanced by ordered surfactant molecular assemblies, dioctadecyldimethylammonium chloride bilayer membrane vesicles, with the largest enhancement factor of 1000 which has not ever been realized. The enhanced emission is further increased by a Mn(II) catalyst with an enhancement factor of ca. 40. The limit of determination(S/N=2) is 1×10^?8M (0.2 ng in 100-μ1 injection), the linear range is four ordrers of magnitude, the sample throughput is 100 h^?1. and the relative standard deviation(n=5) is 0.9 % for 5×10^?7M adrenaline. Of other substances including dopamine, noradrenaline, and related compounds, p-hydroxymandelenic acid chemiluminesces most strongly after adrenaline, the 1×10^?3M solution providing a signal 24% of that for 1×10^?6M adrenaline.     

A New Kinetic-Fluorimetric Method for the Determination of Silver Based on Its Inhibitory Effect on the Oxidation of 2-Hydroxybenzaldehyde Thiosemicarbazone with Hydrogen Peroxide Catalyzed by Iron (III)

Abstract

An indirect kinetic determination of silver based on its inhibitory effect on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone with hydrogen peroxide catalyzed by iron (III) is described. The reaction is followed spectrofluorimetrically by measurement of the initial rate at the wavelengths of the oxidation product (λ_exc=365nm, λ_em=440nm.). The calibration curves are linear between 50-400 ng.ml^?1 of silver with a precision of ± 2.3%. The proposed method has few interferences.     

Kinetic Flow Injection Spectrophotometric Determination of Nitrite by its Catalytic Effect on the Oxidation of Chlorophosphonazo-pN by Bromate

Abstract

A flow injection kinetic method has been developed for the determination of nitrite, based on its catalytic effect on bromate oxidation of chlorophosphonazo-pN in H₂SO₄ medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 551 nm. The sampling frequency was 83 h^?1. The calibration curve was linear between 0.050 and 1.00 μg/ml, and the detection limit was 0.018 μg/ml. The proposed method was applied to the determination of nitrite in waters and soil with satisfactory results.