Kinetic fluorimetric determination of nanogram amounts of manganese, based on its catalysis of the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone with hydrogen peroxide

A kinetic method is described for the determination of trace amounts of manganese(II), based on its catalytic effect on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone by hydrogen peroxide. The reaction is followed by measuring the rate of change of fluorescence (lambda(ex) 365 and lambda(em) 440 nm). The calibration is linear over the manganese range 2-9 ng ml with a precision of +/-1%. The proposed method suffers from few interferences.     

Kinetic fluorimetric determination of silver by its catalytic effect on the oxidation of pyridoxal nicotinylhydrazone by potassium peroxidisulphate

Summary The oxidation of pyridoxal nicotinylhydrazone by potassium peroxidisulphate, catalysed by traces of silver(I), has been studied and used for the kinetic determination of this ion. The reaction is followed spectrofluorimetrically by measuring the rate of change in the fluorescence intensity (_ex 365, _em 450 nm). The calibration graph is linear in the silver range 60–720 ng/ml. The variables affecting the method have been optimized and the tolerance levels of foreign ions determined. The solvent extraction method with dithizone is used to eliminate interferences in the determination of silver in synthetic samples.

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Kinetisch-fluorimetrische Bestimmung von Silber auf der Grundlage seiner katalytischen Wirkung bei der Oxydation von Pyridoxal-nikotinylhydrazon durch Kaliumperoxydisulfat

Zusammenfassung Die durch Silberspuren katalysierte Oxydation wurde untersucht und für deren kinetische Bestimmung verwendet. Die Reaktion wird spektrofluorimetrisch ausgewertet, indem man das Ausmaß der Veränderung der Fluoreszenzintensität (_ex=365, _em=450 nm) bestimmt. Die Eichkurve verläuft für 60–720 ng Ag/ml linear. Die das Verfahren beeinflussenden Reaktionsbedingungen wurden optimiert und die Toleranzgrenzen fremder Ionen bestimmt. Störfaktoren bei der Silberbestimmung in synthetischen Proben wurden durch Extraktion mit Dithizon beseitigt.

     

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.     

Spectrofluorimetric kinetic determination of selenium (IV) by flow injection analysis in cationic micellar medium

A sensitive catalytic kinetic spectrofluorimetric method for determining ng ml(-1) of selenium by flow injection analysis has been developed. The method, based on the catalytic effect of Se (IV) on the reduction of resorufin by sulphide, in the presence of cetylpyridinium chloride, is monitored spectrofluorimetrically (lambda(ex)=480 nm; lambda(em)=583 nm). The linearity range of the calibration graph is dependent on the concentration of sulphide. The variables affecting the rate of the reaction were investigated. The method is simple, rapid, precise, sensitive, and widely applicable. The limit of detection is 1 ng ml(-1) Se (IV), and the calibration range is 5-1000 ng ml(-1). Sampling rate is 60 samples h(-1), and the relative standard deviation of 12 determinations of 100 ng ml(-1) Se was 0.76%. The determination of Se (IV) in the presence of Se (VI) and total selenium is described. The method was applied to the determination of Se in selenium tablets, and several synthetic samples.     

Kinetic spectrophotometric determination of ascorbic acid by reduction of toluidine blue

A simple kinetic method is described for the determination of ascorbic acid. The procedure is based on the reduction of toluidine blue with ascorbic acid. The rate of reaction is followed by measuring the decrease in absorbance of toluidine blue (lambda(max) = 600 nm) as a result of its decolorization upon reduction by ascorbic acid. Ascorbic acid in the range of 3-35 microg/ml was determined using slope and fixed time methods of analysis, while the variable time method allowed the determination of 5-50 microg/ml of ascorbic acid. The percent relative standard deviation of the method varied from 0.78 to 1.32% depending on the kinetic method used. The high sensitivity of the method also allows determination of low levels of ascorbic acid in some fruits and vegetables such as dew melon, water melon, parsley and coriander.     

Utility of oxidation-reduction reaction for the determination of ranitidine hydrochloride in pure form,in dosage forms and in the presence of its oxidative degradates

Three simple, accurate and sensitive colorimetric methods (A, B and C) for the determination of ranitidine HCl (RHCl) in bulk sample, in dosage forms and in the presence of its oxidative degradates are described. The first method A is based on the oxidation of the drug by N-bromosuccinimide (NBS) and determination of the unreacted NBS by measurement of the decrease in absorbance of amaranth dye (AM) at a suitable lambda(max)=520 nm. The methods B and C involve the addition of excess Ce(4+) and determination of the unreacted oxidant by decrease the red color of chromotrope 2R (C2R) at a suitable lambda(max)=528 nm for method B or decrease the orange pink color of rhodamine 6G (Rh6G) at a suitable lambda(max)=526 nm for method C. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 0.2-3.6, 0.1-2.8 and 0.1-2.6 microg ml(-1) for methods A, B and C, respectively. The apparent molar absorptivity. Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.3-3.4, 0.2-2.6 and 0.2-2.4 microg ml(-1) for methods A, B and C, respectively. Analyzing pure and dosage forms containing RHCl tested the validity of the proposed methods. The relative standard deviations were 相似文献   

Kinetic-spectrophotometric determination of trace amounts of silver using the oxidation of thionine with peroxodisulfate.

A simple, rapid and sensitive method has been developed for determination of traces of silver(I) (0.2 - 13 ng mL(-1)) based on its catalytic effect on the oxidation of thionine by peroxodisulfate in the presence of 1 - 10 phenanthroline as an activator. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 600 nm by the fixed time method. The detection limit is 0.098 ng mL(-1) and the relative standard deviation for 0.5, 3.0, 5.0 and 10 ng ml(-1) Ag(I) are 4.1, 1.37, 1.06 and 0.64%, respectively. The method is free from most interferences and it was applied to determination of silver in photographic solutions and well-water samples.     

Kinetic spectrophotometric method for the determination of trace amounts of oxalate by an activation effect.

A new, simple and inexpensive kinetic catalytic spectrophotometric method for the determination of oxalate is described. The method is based on an activation effect of oxalate on a catalytic effect of iron(II) on the oxidation of iodide by bromate. The reaction is monitored by measuring the absorbance of triiodide ion at lambda max = 352 nm. A calibration graph was obtained from 0.10 - 7.0 microg cm(-3) of oxalate with a detection limit of 0.080 microg cm(-3). The standard deviations for ten replicate determinations of 0.50, 1.0 and 5.0 microg cm(-3) of oxalate were 4.0, 2.6 and 1.8%, respectively. The applicability of the method was demonstrated by the determination of oxalate ion in real samples.     

Analytical applications of the o-dianisidine-persulfate reaction: Kinetic determination of silver and cobalt

A kinetic method for the silver determination based on the catalytic effect of Ag(I) on the oxidation of o-dianisidine by persulfate at pH = 4.5 in the presence of 1,10-phenanthroline is proposed. Ag(I) can be determined by measuring the absorbance of the reaction product at 450 nm, using the fixed time method. Co(II) does not have a catalytic effect in the reaction, but in the simultaneous presence of silver and cobalt the reaction shows an induction period the length of which is related to the Ag/Co molar ratio. As a consequence, two new methods for the determination of cobalt and silver using the induction period method are proposed. The two methods for silver are applied to the determination of silver in lead.     

Preconcentration of trace copper with yeast for river water analysis

A sensitive and selective method has been introduced for the determination of ultra trace amounts of Ru(III) based on its catalytic effects on the oxidation of Brilliant green (BG) by sodium bromate. A flow injection method has been used with spectrophotometric detection. The method is based on measuring the decrease in absorbance of BG at lambda(max)=615 nm. The decrease in absorbance of BG is linear with the concentration range of 0.005-0.500 mug ml(-1) Ru(III). The limit of detection is 0.002 mug ml(-1). The influence of reagent concentration, manifold parameter and potential interference species has been investigated. The method was used for the determination of ruthenium in synthetic samples with satisfactory results.     

Flow injection determination of iron by its catalytic effect on the oxidation of 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide

A flow injection-photometric method has been developed for the determination of iron(II+III). The method is based on the catalytic effect of iron(III) on the hydrogen peroxide oxidation of 3,3',5,5'-tetramethylbenzidine to form a blue compound (lambda(max)=650 nm). In this catalyzed reaction, 1,10-phenanthroline acted as an effective activator. Iron(II) is also determined, being oxidized by hydrogen peroxide. Calibration graphs for iron(II) and iron(III) obtained under the optimized conditions were identical with each other and linear in the range 0.2-200 ng ml(-1) with a detection limit of 0.05 ng ml(-1) iron. The reproducibility was satisfactory with a relative S.D. of 1.0% for ten determinations of 5 ng ml(-1) iron(III). The proposed method was successfully applied to the determination of iron in river and lake water samples and can be determined free iron species.     

A simple and rapid fluorimetric method for the microdetermination of isonicotinic acid hydrazide

A simple, rapid and sensitive fluorimetric method has been developed for the microdetermination of isonicotinic acid hydrazide, based on its formation of a hydrazone with 2-hydroxy-1-naphthaldehyde in acidic medium, in the presence of excess of scandium ions, and the consequent formation of a strongly fluorescent complex (lambda(ex) 430 nm, lambda(em) 510 nm) between the hydrazone and scandium in weakly acidic medium. Kinetic and equilibrium procedures for isonicotinic acid hydrazide determination are proposed. A calibration graph linear up to 5.00 mug/ml is obtained by both procedures, with a mean relative error of about 2.0%. The detection limit for the kinetic procedure is 0.4 ng/ml and for the equilibrium procedure about 0.2 ng/ml.     

Spectrofluorimetric determination of acrivastine in spiked human urine and pharmaceuticals

A spectrofluorimetric method to determine acrivastine is proposed and applied to its determination in human urine and pharmaceuticals. The fluorimetric method allows the determination of 58-2000 ng ml(-1) of acrivastine in aqueous solutions containing acetic acid-sodium acetate buffer (pH 6.5) with lambda(exc)=230 nm and lambda(em)=380 nm.     

Kinetic spectrophotometric determination of nanogram amounts of cyanide

A sensitive kinetic method for determination of nanogram amounts of cyanide is reported. It is based on the measurement of the induction period imposed by cyanide on the copper(II)-catalysed oxidation of 3-hydroxybenzaldehyde azine (3-OHBAA) by potassium peroxydisulphate. Kinetic data are recorded spectrophotometrically at 465 nm, the maximum absorption wavelength of the oxidation product of 3-OHBAA. From the kinetic study and other experimental tests it may be concluded that the cyanide ion undergoes copper(II)-catalysed oxidation during the induction period. The calibration plot is linear in the range 150-600 ng/ml cyanide and the detection limit is 50 ng/ml. The precision of the method, expressed as the relative standard deviation, is 3.2% for 350 ng/ml cyanide. Good recoveries are obtained in applying the method to analysis for cyanide in water samples.     

Simultaneous kinetic spectrophotometric determination of vanadium(V) and iron(III)

Vanadium(V) and iron(III) can be determined simultaneously at pH 2 and 25 degrees C by a single experiment using their kinetic effect on the oxidation of indigo carmine by bromate which goes through an induction period and then decreases in absorbance, at lambda(max), 612 nm. The rate of the color-fading of indigo carmine is proportional to the concentration of vanadium and is independent of the concentration of iron. The length of the induction period of the reaction is related to the concentration of iron and is independent of the concentration of vanadium. Concentrations of 0.3-2 (mug ml(-1)) vanadium(V) and 6-12 (mug ml(-1)) iron(III) were determined with mean relative errors of 2.7 and 1.6%, respectively. The interference effects of various cations and anions on determination of mixtures of vanadium and iron is reported. Application of the method to real samples and several mixtures of standard solutions are performed which gave acceptable results.     

Improved spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol in the presence of benzyldimethylstearyltrimethylammonium chloride

An improved spectrophotometric determination of uranium(VI) is proposed using 4-(2-pyridylazo)resorcinol(PAR) in the presence of benzyldimethylstearyltrimethylammonium chloride(BSTAC) as a cationic surfactant. The calibration graph is linear in the range of 0.3-60 microg/10 ml uranium(VI), measuring the absorbance at 550 nm. The reproducibility for 19.0 microg/10 ml uranium(VI) is 0.57%. The third-derivative method using the third-derivative distance (d(3)A/dlambda(3)) among lambda(1) 530 nm, lambda(3) 594 nm and lambda(2) 565 nm was also investigated.     

Catalytic-kinetic determination of trace amount of formaldehyde by the spectrophotometric method with a bromate-Janus green system

A new simple and rapid catalytic kinetic method for the determination of trace amount of formaldehyde is described. The method is based on the catalytic effect of formaldehyde on the oxidation of Janus green by bromate in the present of sulfuric acid. The reaction monitored spectrophotometrically by measuring the decrease in absorbance of the reaction mixture at 618 nm. The fixed-time method was used for the first 150 s. For initiation of the reaction, under the optimum conditions, in the concentration range of 0.003-2.5 microg ml(-1) formaldehyde can be determined with a limit of detection 0.0015 microg ml(-1). The relative standard deviation of five replicate measurements is 2.3% for 1.0 microg ml(-1) of formaldehyde. The method was used for the determination of formaldehyde in real samples with satisfactory results.     

Catalytic determination of traces of silver(I) using the oxidation of Janus Green with peroxodisulfate.

A method for sensitive and selective determination of silver based on the catalytic effect of silver(I) ion on the oxidation of Janus Green by peroxodisulfate is described. o-Phenanthroline is used as an activator. The rate of the decrease in absorbance of Janus Green (at 615 nm) is proportional to the concentration of silver in the range of 0.3-4.0 ng mL(-1) and 4.0-500.0 ng mL(-1). The theoretical limit of detection was 0.25 ng mL(-1). The method is free from most interferences. The method was applied to the determination of silver in plants (the uptake of silver by plants), in photographic solutions, lake water and several synthetic samples.     

Catalytic kinetic determination of ultratrace amounts of ruthenium(III) based on the oxidation of benzylamine by alkaline hexacyanoferrate(III)

A kinetic method is proposed for the determination of ruthenium(III) by means of its catalytic effect on the oxidation of benzylamine by hexacyanoferrate(III) in alkaline medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance of hexacyanoferrate(III) at 420 nm. Under the optimum experimental conditions ruthenium(III) can be determined in the range 10-121 ng/ml with an average error of 1.7% and maximum relative standard deviation of 1.3%. The influence of many potential interferents has been examined and the method has been tested for determination of ruthenium(III) in synthetic mixtures. The method is convenient, reliable and rapid.     

New computational approach for the simultaneous photometric determination of catalysts and activators

A new method for the simultaneous kinetic determination of catalysts and activators was developed on the basis of a mathematical model. The parameters and variables are optimized from experimental data obtained by application of a multiple standard-addition method and use of the Gauss-Newton and Simplex method, both of which provide identical results. The proposed method was applied to the simultaneous photometric determination of Mn(II) and Pb(II) on the basis of their catalytic and activating effects, respectively, on the oxidation of Tiron by hydrogen peroxide. Data were both acquired and processed with the aid of software developed by the authors. The linear determination range achieved was 1.00-5.00 ng/ml Mn(II) and 200-800 ng/ml Pb(II). Experimental readings were made at 450 nm with a fibre optics detector. The most serious interference with the method was posed by Cr(III).