Spectrofluorimetric determination of hydrogen peroxide based on the catalytic effect of peroxidase-like manganese tetrakis(sulphophenyl) porphyrin on the oxidation of homovanillic acid

Traces of hydrogen peroxide (8.5 × 10^?8–2.5 × 10^?6 mol/l) and, indirectly, glucose (3–44 × 10^?6 mol/l) can be determined by the fluorescence reaction between homovanillic acid and hydrogen peroxide. Mn-TPPS₄ is found to have very similar catalytic properties to horse peroxidase.     

Spectrofluorimetric determination of traces of perchlorate by extraction with rhodamine 6G

A method for the spectrofluorimetric determination of perchlorate is described; it is based on extraction of the perchlorate-Rhodamine 6G ion-pair into benzene. The procedure is sensitive, highly reproducible and useful for the determination of 0.04-1.0 ppm of perchlorate. The determination of traces of perchlorate in chlorate is described.     

Spectrophotometric determination of osmium based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide

A highly sensitive spectrophotometric method is described for the determination of trace amounts of osmium(VIII), based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 540 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1x10(-4) mol l(-1) carminic acid, 0.013 mol l(-1) hydrogen peroxide and pH 10 at 25 degrees C. By using the recommended procedure, the calibration graph was linear from 0.1 to 1.5 ng ml(-1) of osmium; the detection limit was 0.02 ng ml(-1); the RSD for five replicate determinations of 0.2-1.4 ng ml(-1) was in the range of 1.8-4.7%. The influence of several foreign ions on osmium determination were studied and the effect of interfering ions were removed by extracting osmium into isobuthyl methyl ketone and back extracting into sodium hydroxide solution.     

Kinetic determination of traces of manganese(II) by its catalytic effect on the oxidation of acid blue 45 with hydrogen peroxide

A catalytic method is described for the determination of trace amounts of manganese(II) based on its catalytic effect on the hydrogen peroxide oxidation of an anthraquinone dye, Acid blue 45 (C.I. 63010). The reaction is followed spectrophotometrically by measuring the rate of change in absorbance of the dye at 595 nm. The calibration graph (rate constant (tg α) vs. manganese concentration) is linear in the range 4–25 ng Mn ml^?1, the relative standard deviation being 1.9% at the 13 ng Mn ml^?1 level. There are few interferences. The kinetic parameters of the reaction were investigated and the role of hydrogen peroxide and hydrogencarbonate ions is discussed.     

Spectrofluorimetric determination of picogram level Pb(II) using a dimercaptothiadiazole fluorophore

This paper describes the spectrofluorimetric determination of picogram level Pb(II) using 2,5-dimercapto-1,3,4-thiadiazole (DMT) as a fluorophore. Excitation of DMT at 330 nm shows an emission maximum at 435 nm. The colorless solution of DMT changes into highly emittive yellow color immediately after the addition of 0.5 μM Pb(II) and nearly 245-fold increase in emission intensity at 435 nm was observed. These changes were attributed to the complex formation between Pb(II). The emission intensity linearly increases in the concentration range of 10–100 nM Pb(II) and DMT. Based on the fluorescence enhancement, the concentration of Pb(II) was determined. Interestingly, the emission intensity was increased even in the presence of 0.1 pM Pb(II). The fluorophore showed an extreme selectivity towards 100 nM Pb(II) even in the presence of 50,000-fold higher concentrations of common metal ions interferences such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe²⁺, Cd²⁺, Cr³⁺, Mn²⁺, Zn²⁺, Co²⁺, Ni²⁺ and 5000-, 100- and 40-fold of Cu²⁺, Hg²⁺ and Ag⁺ ions, respectively. The lowest detection of 20 pg L⁻¹ Pb(II) was achieved for the first time using DMT. The proposed method was successfully utilized for the determination of Pb(II) in tap water, polluted river water and industrial waste water samples. The results obtained in the present study were validated with both AAS and ICP-AES methods.     

Chemiluminescence of chlorpromazine hydrochloride based on cerium(IV) oxidation sensitized by rhodamine 6G

A new chemiluminescence (CL) method is proposed for the determination of chlorpromazine hydrochloride, a drug often used to treat the psychiatric patients suffering from clinical depression. The method is based on the reaction between studied drug and Ce(IV) in a nitric acid medium and measurement of the CL intensity produced by rhodamine 6G used as a sensitizer. In the optimum conditions, CL intensities are proportional to concentrations of the studied drug over the range 0-1x10(-5) g ml(-1) with a detection limit of 6.5x10(-9) g ml(-1). The relative standard deviation (R.S.D.) is 4.1% for 1.5x10(-6) g ml(-1) chlorpromazine hydrochloride (n=11). The method has been applied to the determination of studied drug in tablets and biological fluids with satisfactory results.     

Kinetic spectrophotometric method for the determination of urinary cobalt based on its catalytic effect on the oxidation of -adrenaline hydrochloride by hydrogen peroxide

A catalytic for determination of nanomolar concentrations of Co(II), i.e., oxidation of -adrenaline hydrochloride with H₂O² in alkaline medium, is proposed. The reaction gives a low limit of detection of 2.5 × 10 ⁻⁹ M Co(II) in the reaction mixture, good reproducibility with a relative standard deviation (R.S.D.) of 4−5% in the Co(II) concentration range 8.0 × 10⁻⁹−8.0 × 10⁻⁸M and good selectivity. On the basis of this indicator reaction, a catalytic-spectrophotometric method for the determination of cobalt in small urine samples (5.00 ml) was elaborated. The analysis of 17 urine samples, taken from healthy persons of different ages, gave cobalt concentrations in the range 0.20–1.50 μmol 1⁻¹. The R.S.D. for ten replicate analyses of a urine sample with an average cobalt content of 0.63 μmol 1⁻¹ was 5.6%. The reliability of the method was verified by a comparative photometric method (r = 0.9755) and by a determination based on known additions of cobalt (r = 0.9894).     

Copper(II) determination by means of a thermometric method based on its catalytic effect on the hydrazine-hydrogen peroxide reaction

A new catalytic-thermometric method for Cu(II) determination at ppb levels has been established based on the hydrazine-hydrogen peroxide redox reaction. The reaction rate is obtained from the temperature-time curve and shows two linear response zones, between 15–200 ppb and 0.1–0.9 ppm, with a relative standard deviation of 2.0% and 2.2%, respectively. Only 20 ppm of Pb(II) and Fe(III), 1 ppm of Mn(II) and 5 ppb of Co(II) interfere. Interferences of Pb(II) and Fe(III) can be eliminated by the use of maskings. The proposed method can be applied to determine Cu(II) in several samples. In the present paper, this method has been applied to determine Cu(II) in wine.     

Kinetic-spectrophotometric determination of palladium in hydrogenation catalyst by its catalytic effect on the oxidation of pyrogallol red by hydrogen peroxide

A new kinetic-spectrophotometric method is described for the determination of ultra trace amounts of Pd(II). The methods based on catalytic action of Pd(II) on the oxidation of pyrogallol red (PGR) with hydrogen peroxide at pH 9.7. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of the PGR at 540 nm, for the first 4.5 min from initiation of the reaction. Calibration curve was linear in the range of 0.02-1.00 microg ml(-1) Pd(II). The limit of detection is 0.017 microg ml(-1) Pd(II). The relative standard deviation (R.S.D.) for ten replicate analyses of 0.03 and 0.60 microg ml(-1) Pd(II) was 1.5 and 0.9%, respectively. The influence of more than 40 potential interfering ions was studied for the selectivity. The proposed method was used for the determination of palladium in catalytic material.     

Kinetic determination of traces of copper(ii) by its catalytic effect on the oxidation of 4,4'-dihydroxy-benzophenone thiosemicarbazone by hydrogen peroxide

The kinetic method is based on the catalytic effect of copper(II) on the oxidation of 4,4'-dihydroxybenzophenone thiosemicarbazone by hydrogen peroxide. The reaction is followed spectrophotometrically at 415 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. Three methods of rate measurement are compared. The calibration graphs are linear in the range 10–90 ng Cu ml^-1. There are few interferences. The method is applied to the determination of copper in waters.     

Spectrophotometric kinetic determination of copper(II) trace amounts based on its catalytic effect on the reaction of the reduced 2,6-dichlorophenolindophenol and hydrogen peroxide

A catalytic spectrophotometric method is presented for the determination of Cu(II), based on the oxidation of the leucocompound of the 2.6-dichlorophenolindophenol (DCPI)(r), in the presence of hydrogen peroxide and the catalytic effect of Cu(II) on this reaction in ammonia-ammonium chloride buffer solution of pH 10.5. The above reaction is followed spectrophotometrically at 562 nm. The study was carried out with a filter spectrophotometer equipped with a fiber optic and an immersed type optical cell of 1 cm. The optimum operating conditions regarding concentration of the reagents involved, pH and temperature were established. The interference effect of several metallic species was also investigated. It was found that the proposed method shows fairly good selectivity and sensitivity, simplicity and rapidity compared to other kinetic methods. The working curve of the recommended reaction-rate method is linear in the concentration range 5-300 ng/ml. The relative standard deviation for a standard solution of 30 ng/ml Cu(II) is better than 2.5%. The method was applied successfully on the determination of Cu(II) in a wide variety of real samples such as alloys, pharmaceuticals, foodstuffs and environmental samples. The results were compared to those received with official methods. Good agreement was attained.     

Catalytic determination of nanogram amounts from iron(III) using its catalytic effect on the oxidation of sodium pyrogallol-5-sulphonate by hydrogen peroxide

A kinetic method is described for the determination of iron(III) based on its catalytic effect on the oxidation of sodium pyrogallol-5-sulphonate by hydrogen peroxide. The reaction was followed spectrophotometrically by measuring the rate of change in the absorbance of the coloured product at 436.8 nm. Nanogram amounts of iron(III) (2.0-75.0 ng cm(-3)) can be determined with good accuracy and reproducibility. The influence of foreign ions on the results was investigated and the method was found to be adequately selective. It has been applied satisfactorily to the determination of iron(III) in tap water samples. The kinetic parameters of both the catalysed and uncatalysed reactions are reported.     

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 kinetic determination of ultramicro quantities of manganese(II), molybdenum(VI) and tungsten(VI) on the basis of their catalytic action on the oxidation of Azorubin S by hydrogen peroxide

Summary A study has been made of the kinetics of catalytic oxidation of Azorubin S by hydrogen peroxide in the presence of Mn(II), Mo(VI) and W(VI) in order to find optimal conditions for the kinetic catalytic determination of these elements. Manganese(II), molybdenum(VI) and tungsten(VI) were determined in the concentration ranges 5.5–33.0×10^–3, 1.3–8.1 and 5.9–44.1g/ml, respectively. Standard deviations were less than 11%. The effect of some foreign ions on these determinations was also investigated.

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Zusammenfassung Die Kinetik der katalytischen Oxydation von Azorubin S mit Wasserstoffperoxid in Anwesenheit von Mn(II), Mo(VI) und W(VI) wurde untersucht, um die optimalen Bedingungen für deren kinetisch-katalytische Bestimmung zu finden. Mn(II) wurde im Konzentrationsbereich von 5,5–33,0×10^–3, Mo(VI) von 1,3–8,1 und W(VI) von 5,9–44,1g/ml mit Standardabweichungen <11% bestimmt. Außerdem wurden einige der möglichen Störungen untersucht.

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This work was presented in part at the 20th Annual Meeting of the Serbian Chemical Society, Belgrade, January 17, 1977.     

Determination of copper by its catalytic effect on the oxidation of hydroquinone by hydrogen peroxide on supports

The reaction of oxidation of hydroquinone by hydrogen peroxide catalyzed by copper(II) in the presence of 2,2’-dipyridyl is activated by hexamethylenediamino groups that are bonded to the surface of filter paper; additional activating effect is produced by 2,2′-dipyridyl. The introduction of malonic acid dinitrile into the indicator reaction improves the sensitivity of the determination of copper and the contrast of the reaction in solution because of the formation of a blue product. Differently colored compounds are formed on a paper support at different concentrations of copper, which makes it possible to visually distinguish the quantities of copper that differ by an order of magnitude in the range 1 × 10^-5-0.5 μg. Quantitative detection is possible in the range 5 × 10^-6-0.1 μg (c_min = 3 × 10^-6 μg). The concentration of copper (0.2-1.5 μg/mL) is determined in blood serum; the consumption of the sample per one determination is 3 μL     

Application of rhodamine B hydrazide as a new fluorogenic indicator in the highly sensitive determination of hydrogen peroxide and glucose based on the catalytic effect of iron(III)-tetrasulfonato-phthalocyanine

A sensitive, selective and rapid spectrofluorimetric method is proposed for the determination of hydrogen peroxide using rhodamine B hydrazide as a fluorogenic substrate catalyzed by iron(III)-tetrasulfonatophthalocyanine. It is based on the oxidation of rhodamine B hydrazide, a colorless, non-fluorescent spirolactam hydrazide, by hydrogen peroxide which generates the highly fluorescent product rhodamine B. Under optimum conditions, the responses for hydrogen peroxide were linear from 2.0 × 10⁻⁸ to 2.0 × 10⁻⁶ mol L⁻¹, with a detection limit of 3.7 × 10⁻⁹ mol L⁻¹ in a 3.5 min reaction period. It can easily be incorporated into the determination of biochemical substances that produce hydrogen peroxide under catalytic oxidation in the presence of their oxidase. The possibility has been tested for the determination of glucose in human sera as an example.     

Kinetic determination of traces of iodide by its catalytic effect on oxidation of sodium pyrogallol-5-sulfonate by hydrogen peroxide.

The kinetic method is based on a catalytic effect on the oxidation of sodium pyrogallol-5-sulfonate by hydrogenperoxide. The reaction is followed spectrophotometrically at 436.8 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. The calibration graph is linear in the range 10-200 ng cm(-3). The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. This method has high sensitivity and good selectivity when anions are concerned as well. That is why it can be successfully applied to determination of iodide in real samples (mineral water and soil) directly after the elimination of cations, which interfere. The method was applied to determine iodide in natural waters and soil.     

Catalytic kinetic determination of ultratrace amounts of ruthenium(III) based on the oxidation of hematoxylin by hydrogen peroxide

A new catalytic method was described for the determination of ruthenium(III) based on its catalytic effect on the oxidation of hematoxylin by hydrogen peroxide in weakly acidic medium. The reaction was followed spectrophotometrically by measuring the absorbance of hematoxylin at 440 nm. Under the optimum conditions, ruthenium(III) can be determined in the range 5–120 ng/ml with a relative standard deviation of 1.1%. The mean value of reaction rate constant was 0.012±0.04 min^–1 and the activation energy was 10.45 kJ/mol. The method was tested for the determination of ruthenium(III) in some synthetic mixtures.     

Spectrophotometric reaction rate method for the determination of molybdenum by its catalytic effect on the oxidation of pyrogallol red with hydrogen peroxide

A kinetic spectrophotometric method for the determination of molybdenum is based on its catalytic effect on the oxidation of pyrogallol red with hydrogen peroxide. The decrease of the absorbance of pyrogallol red in the presence of hydrogen peroxide with time from 0.5 to 4.5 min is proportional to the concentration of Mo(VI) over the range 0.010–0.500 μg/mL. The limit of detection is 0.008 μg Mo/mL. The precision and the effect of the presence of more than forty ions on the molybdenum determination are reported. Probable interferences are completely removed by a cation exchange resin. The procedure was successfully applied to the determination of molybdenum in plant materials and steels. Received: 28 April 1997 / Revised: 16 June 1997 / Accepted: 18 June 1997     

A kinetic method for the determination of copper(II) by its catalytic effect on the oxidation of 3-methyl-2-benzothiazolinone hydrazone with hydrogen peroxide: a mechanistic study.

A catalytic spectrophotometric method for the determination of traces of copper(II) is proposed. 3-Methyl-2-benzothiazolinone hydrazone (MBTH) is oxidized by hydrogen peroxide to form a yellowish-brown compound. The reaction is accelerated by trace amounts of copper(II), and can be followed by measuring the increase in the absorbance at 390 nm. Since the absorbance at 40 min from the reaction start increases with an increase in the copper(II) concentration, the absorbance value is used as a parameter for copper(II) determination. Under the optimum experimental conditions (8.4 x 10(-3) mol dm(-3) MBTH, 0.7 mol dm(-3) hydrogen peroxide, pH 5.2, 35 degrees C), copper(II) can be determined in the range 0-50 microg dm(-3). The relative standard deviations are 6.9, 3.5, 2.7% for 2, 20 and 40 microg dm(-3), respectively. The detection limit of this method (3sigma) is 0.27 microg dm(-3). It was successfully applied to a determination of copper(II) in river water, tap water and ground-water samples. According to the results of a kinetic study, a mechanism is proposed which leads to the following rate equation: R0(cat) = kK1K2[MBTH][H2O2][Cu(II)]0/{(1 + K2[H2O2])[H+]}.