Spectrophotometric and spectrodensitometric determination of paracetamol and drotaverine HCl in combination

Thin-layer chromatography, first derivative, ratio spectra derivative spectrophotometry and Vierordt's method have been developed for the simultaneous determination of paracetamol and drotaverine HCl. TLC densitometric method depends on the difference in Rf values using ethyl acetate:methanol:ammonia (100:1:5 v/v/v) as a mobile phase. The spots of the two drugs were scanned at 249 and 308 nm over concentration ranges of 60-1200 microg/ml and 20-400 microg/ml with mean percentage recovery 100.11%+/-1.91 and 100.15%+/-1.87, respectively. The first derivative spectrophotometric method deals with the measurements at zero-crossing points 259 and 325 nm with mean percentage recovery 99.25%+/-1.08 and 99.45%+/-1.14, respectively. The ratio spectra first derivative technique was used at 246 and 305 nm with mean percentage recovery 99.75%+/-1.93 and 99.08%+/-1.22, respectively. Beer's law for first derivative and ratio spectra derivative methods was obeyed in the concentration range 0.8-12.8 and 0.4-6.4 microg/ml of paracetamol and drotaverine HCl, respectively. Vierordt's method was applied to over come the overlapping of paracetamol and drotaverine HCl in zero-order spectra in concentration range 2-26 and 2-40 microg/ml respectively. The suggested methods were successfully applied for the analysis of the two drugs in laboratory prepared mixtures and their pharmaceutical formulation. The validity of the methods was assessed by applying the standard addition technique. The obtained results were statistically agreed with those obtained by the reported method.     

Voltammetric determination of dinitrotriethylbenzene

It was shown that dinitrotriethylbenzene can be determined by voltammetry at mercury-film and glassy-carbon electrodes. A procedure for determining dinitrotriethylbenzene at a glassy-carbon electrode in a reaction mixture was developed.     

Voltammetric determination of buspirone

The electroanalytical chemical properties of buspirone are reported in this paper. A sensitive single sweep voltammetric procedure for trace buspirone determination was developed. The detection limit is 5.0 x 10(-9)M. The method has been applied to the determination of buspirone in blood serum by simple dilution in a buffer.     

Voltammetric study and determination of cacotheline

The polarographic and cyclic voltammetric characteristics of cacotheline at mercury electrodes are reported. Two well-defined, diffusion-controlled cathodic peaks are observed over the pH range 2.03—12.0. The electrode process involves two electrons for the reversible reduction of the o-quinone group to hydroquinone folloed by a four-electron irreversible reduction of the nitro group to hydroxylamine. The effects of experimental variables on the characteristics of the waves are described. The reduction mechanism is elucidated from the results of constat-potential coulometry and infrared spectroscopy.     

Voltammetric determination of methidathion insecticide

An electroanalytical method has been developed for the determination of methidathion by squarewave voltammetry on a Nafion®-coated glassy carbon electrode in aqueous solutions with 0.05 M acetate buffer as a supporting electrolyte. The best voltammetric conditions were found to be pH 4.0, a preconcentration potential of 0.45 V, and a preconcentration time of 60 s. The experimental parameters, such as pH, film thickness, preconcentration potential, preconcentration time, and square-wave voltammetric parameters, were optimized. Using this method, the calibration curve is linear in the range 5 × 10^?8?7 × 10^?7 M with a detection limit (S/N = 3) of 30 nM.     

Voltammetric determination of chlorpromazine hydrochloride

The electrochemical behaviour of chlorpromazine hydrochloride (CPZ-HCI) in sulphuric acid was investigated voltammetrically using ruthenium electrodes and it was subsequently determined by the same method. From the recorded voltammograms it was concluded that CPZ-HCI can be determined in the concentration range 2 x 10(-4)-8 x 10(-4) M (71-284. 3 micrograms ml-1). The proposed voltammetric method was applied to the determination of CPZ-HCI in tablets used for neuroleptic purposes in Turkey; the amount of effective compound was found to be within the ranges given for a pharmacopoeial procedure.     

A kinetic determination of ultramicroquantities of papaverine

A kinetic method for the determination of ultramicroquantities of papaverine based on its activator action on the reaction between hydrogen peroxide and cobalt(II) in carbonate buffer solution is presented. Kinetic equations of the reaction studied in the presence of and in the absence of papaverine were postulated and their apparent rate constants, activation energies, and thermodynamic parameters were calculated. The reaction rates were followed photometrically. Papaverine was determined in concentrations ranging from 1.0 to 12.0 μg/ml, with relative standard deviation from 1.8 to 8.5%. The effect of related substances from the opium alkaloid group on this determination was estimated. The described method was applied for the determination of papaverine in urine samples as well.     

Voltammetric determination of Tartrazine in food

A possibility of using voltammetry for the direct determination of yellow synthetic food dye Tartrazine, included in the list of substances regulated in food, is demonstrated. The electrochemical behavior of the dye is studied by direct current voltammetry using a glassy carbon electrode. It is shown that the signal of Tartrazine electrochemical reduction is the most pronounced in an acidic medium at pH 2.0, accumulation potential of 0.1 V, and time of 10 s. The dependence of the electrochemical reduction current of the dye at a potential of–0.25 V on its concentration is linear in the range 0.05–0.50 mg/L with the determination limit 0.034 mg/L and detection limit 0.011 mg/L. A procedure for quantifying the dye in food is proposed.     

Voltammetric determination of agriculturally-significant benzenearsonic acids

Direct current and differential pulse polarographic measurements are reported on a series of substituted benzenearsonic acid compounds that are important in agricultural applications. Compounds studied were o-aminobenzenearsonic acid, p-aminobenzene-arsonic acid, p-nitrobenzenearsonic acid, p-ureidobenzenearsonic acid, and 3-nitro-4-hydroxybenzenearsonic acid. Polarographic reduction potentials varied with pH for all compounds, shifting to more negative values as the pH was increased. Although diffusion-controlled reduction waves were observed in all cases, some compounds exhibited a dependence of E$\text{1}\text{2}$ on concentration, especially at relatively high concentrations. Differential pulse polarographic peak currents were proportional to concentration from 10^-4 M to 10^-6 M.     

Voltammetric determination of curcumin in spices

Curcumin is oxidized on a glassy carbon electrode in 0.1 M LiClO₄ in ethanol at the potential 0.74 V. The calibration graph is linear in the range 9.9 × 10^?6?1.07 × 10^?4 M curcumin; the detection limit is 4.1 × 10^?6 M. Curcumin is determined in model solutions. The relative standard deviation does not exceed 0.05. A procedure is proposed for the voltammetric determination of curcumin in spices. It was shown that single extraction by ethanol quantitatively recovers curcumin from spices.     

Voltammetric determination of molybdenum in brines

Summary The presence of molybdenum in natural water, at the ng/ml level, is essential for the growth of phytoplankton and other organisms, but its presence in brines is reported to affect the current efficiency in electrochemical chlor-alkali production. A voltammetric method, incorporating a preconcentration step, has been developed for the determination of molybdenum at this level in brine and sea-water. Molybdenum is co-precipitated with cadmium sulphide at a pH of about 2. The precipitate is dissolved in aqua regia and fumed with perchloric acid. The residue is dissolved in a supporting electrolyte comprising 1M sodium perchlorate, 0.1M sodium acetate and 0.01M EDTA (pH 6.0±0.2). At this pH, a well-defined wave for the reduction of molybdenum(VI) is obtained at –0.88 Vvs. SCE. None of the common ions interferes. Preconcentration of the molybdenum from 1 litre of brine facilitates its determination down to 1 ng/ml. The estimated precision at the 5 ng/ml level is 13%.

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Voltammetrische Molybdänbestimmung in Salzwasser

Zusammenfassung Die Anwesenheit von Molybdän in natürlichem Wasser in der Größenordnung von ng/ml ist für das Wachstum von Phytoplankton und anderen Organismen wesentlich, aber, wie berichtet wird, stört seine Anwesenheit in Salzwässern die elektrochemische Produktion von Chlor bzw. Alkali. Eine voltammetrische Methode mit vorangehender Anreicherung wurde für die Molybdänbestimmung in dieser Größenordnung in Salz- und Meerwasser ausgearbeitet. Molybdän wird bei pH etwa 2 mit Cadmiumsulfid mitgefällt. Dieser Niederschlag wird in Königswasser gelöst und mit Perchlorsäure abgeraucht. Der Rückstand wird in einem Trägerelektrolyt mit 1M Natriumperchlorat, 0,1M Natriumacetat und 0,01M ÄDTA (pH 6,0±0,2) gelöst. Bei diesem pH erhält man bei –0,88 V gegen eine ges. Kalomelelektrode für die Reduktion von Mo(VI) eine wohldefinierte Welle. Keines der üblichen Ionen stört. Die Anreicherung des Molybdäns aus 1 Liter Salzwasser erleichtert seine Bestimmung bis zu 1 ng/ml. Die geschätzte Genauigkeit für die Größenordnung 5 ng/ml beträgt 13%.

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Presented at the 8th International Microchemical Symposium, Graz, August 28, 1980.     

Voltammetric and amperometric determination of 2,4-dinitrophenol metabolites

Methods for determination of 2-amino-4-nitrophenol and 4-amino-2-nitrophenol, metabolites of 2,4-dinitrophenol, were developed using differential pulse (DP) voltammetry and HPLC with amperometric and spectrophotometric detection. The applicability of these methods was tested by the determination of the analytes in model samples of urine after preliminary separation by solid-phase extraction. Voltammetry enabled parallel determination of both analytes, but its application in real matrix was severely limited due to the interference of other compounds present in urine. HPLC allowed the determination in real urine matrix down to micromolar concentrations; amperometric detection proved to be more sensitive and selective than the spectrophotometric one.     

Voltammetric determination of dipeptidyl aminopeptidases I and IV

Dipeptidyl aminopeptidases I and IV have recently found wide practical application (polypeptide sequencing, clinical diagnostics) so it is necessary to extend present methods and work out new ones for determination of their activity. A new, voltammetric method for determination of peptidase activity is proposed, which allows optimization of the determination conditions according to the activity to be measured. The method has some advantages over the spectrophotometric methods, such as applicability to opaque solutions and higher sensitivity.     

Simultaneous determination of nifuroxazide and drotaverine hydrochloride in pharmaceutical preparations by bivariate and multivariate spectral analysis

The quantitative predictive abilities of the new and simple bivariate spectrophotometric method are compared with the results obtained by the use of multivariate calibration methods [the classical least squares (CLS), principle component regression (PCR) and partial least squares (PLS)], using the information contained in the absorption spectra of the appropriate solutions. Mixtures of the two drugs Nifuroxazide (NIF) and Drotaverine hydrochloride (DRO) were resolved by application of the bivariate method. The different chemometric approaches were applied also with previous optimization of the calibration matrix, as they are useful in simultaneous inclusion of many spectral wavelengths. The results found by application of the bivariate, CLS, PCR and PLS methods for the simultaneous determinations of mixtures of both components containing 2-12microgml(-1) of NIF and 2-8microgml(-1) of DRO are reported. Both approaches were satisfactorily applied to the simultaneous determination of NIF and DRO in pure form and in pharmaceutical formulation. The results were in accordance with those given by the EVA Pharma reference spectrophotometric method.     

Voltammetric determination of thiodiglycolic acid in urine

In urine the level of thiodiglycolic acid (TDGA) is a sensitive indicator of exposure of the human organism to some physiologically active or toxic substances, gases and vapors. The determination of TDGA by use of a voltammetric method based on electroreduction of TDGA in acidic solution at the hanging mercury drop electrode has been developed and practically tested. In order to eliminate the matrix effect of urine, prior to voltammetric measurement the samples are eluted from a small column of PVC powder. The method is simple, low cost, rapid and sensitive, appropriate for the needs of occupational medicine.     

Voltammetric determination of zirconium using azo compounds

The Optimum oconditions for zirconium complexation with azo compounds are found. The applicability of Eriochrome Red B, Calcon, and Calcion to the voltammetric determination of zirconium, total Zr(IV) and Hf(IV), and Zr(IV) in the presence of Zn(II), Cu(II), Cd(II), Ni(II), or Ti(IV) is demonstrated. The developed procedures are used to determine zirconium in a terbium alloy and in an alloy for airplane wheel drums.     

Voltammetric determination of hafnium with calconcarboxylic acid

The interaction of Hf(IV) with calconcarboxylic acid (1-(2-hydroxy-4-sulfo-1-naphtylazo)-3-naphtolic acid) was investigated by cyclic voltammetry varying various factors (pH, ionic strength, contents of ethanol and scan rate). Optimal conditions of Hf(IV) determination in the presence of calconcarboxylic acid were found: acetic buffer solution pH 2.6, scan rate 0.5 Vs⁻¹. The detection limit of Hf(IV) concentration was 2.46 × 10⁻⁷ mol L⁻¹. The influence of foreign ions on the Hf(IV) determination was studied. It was established that some metals like cadmium, nickel, zinc, copper and titanium could be determined with Hf(IV) simultaneously. The method of voltammetric determination of hafnium was tested on model solutions and used in the determination of Hf(IV) in terbium-base alloy.     

Spectrophotometric determination of papaverine hydrochloride by reaction with phloxin

A new withasteroid — vamonolide — has been isolated from the epigeal part ofPhysalis angulata L. (Solanaceae). On the basis of spectral characteristics, its structure has been established as 5,14-dihydroxyl-l-oxo-6,7-epoxy-20R,22R-with-2-enolide.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 856–858, November–December, 1987.     

Spectrophotometric determination of papaverine hydrochloride by reaction with phloxin

The optimum conditions for the formation of a complex of papaverine hydrochloride with phloxin have been determined: pH 2.5–3.2. A procedure has been developed for the spectrophotometric determination of papaverine hydrochloride. The sensitivity of the determination is 0.4 µg/ml.Vitebsk Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 836–838, November–December, 1988.     

Voltammetric determination of nickel and palladium in plating baths

Summary A simultaneous determination of nickel and palladium in plating baths was carried out at the hanging mercury drop electrode (HMDE), using the dc and ac single-sweep techniques, direct in the bath sample diluted with ammonia buffer. The influences of Co, Pb, Zn, Cd and the concentration of ammonia buffer on the peak shapes of Ni and Pd and on their resolution were studied. The possible determination of Cd and Pb contamination in plating baths in the same solution by anodic stripping voltammetry is also indicated. The essential advantages of the described method are: its simplicity, rapidity and very small consumption of mercury. The detailed analytical procedure is given. Relative standard deviations were found to be 3.1% for Pd and 2.6% for Ni.