Kinetic determination of uranium(IV) based on its catalytic effect on the phosphomolybdic acid-iodide reaction

A kinetic spectrophotometric method has been developed for the determination of trace amounts of uranium(IV) based on its catalytic effect on the phosphomolybdic acid iodide reaction. A significant feature of the proposed procedure is the selectivity for uranium(IV); it enables the determination of trace amount of uranium in the presence of large excess of rare metalions and other cations and anions. The method can be applied to the determination of uranium within the concentration range of 0–12μg· cm^?3, and the detection limit of the method is 0.02μg·cm^?3. Trace amounts of uranium in thorium nitrate and scandium oxide had been determined by the procedure and the results are satisfactory.     

Kinetic determination of trace amounts of thiosulfate based on its inhibitory effect

The sulfur containing ligand viz., thiosulfate is found to inhibit the Ag(I) catalyzed substitution of cyanide in hexacyanoferrate(II) by phenylhydrazine. The inhibitory effect of thiosulfate is attributed due to its tendency to form complexes with Ag(I), leading to the production of inhibitor-catalyst complexes. The reactions, followed spectrophotometrically in aqueous medium at 488 nm, was possible by the increase in absorbance of the cherry-red product, [Fe(CN)₅PhNHNH₂]^3- at pH 2.8 (±0.02), at 30 (±0.1) °C, and an ionic strength (μ) of 0.02 M (KNO₃). The linear calibration curves were obtained using the absorbance measured at different times (A_t) and thiosulfate concentrations under specified conditions. The calculated detection limit was 4.9 × 10^-7 M. The Michaelis-Menten constant (K_m) and equilibrium constants for the formation of complexes between catalyst and inhibitor (K_CI), and the catalyst and substrate (K_S) were computed from the kinetic data. A general mechanistic scheme is proposed for this reaction.     

Simultaneous kinetic determination of metal ion mixtures based on a ligand substitution reaction

The rates of the ligand substitution reactions between 2-(4-sulfophenylazo)-l,8-dihydroxy-3, 6-naphthalenedisulfonic acid (SPADNS) complexes of Co²⁺, Ni²⁺, Pb²⁺ and Cu²⁺ and EDTA (or CDTA) have been studied at 25.0°C, pH 8.0–9.3, by stopped-flow spectrophotometry. The reactions are first order in SPADNS complex and in incoming ligand. The absorbance change during the reaction progress can be kinetically separated for each component of a mixture, so that metal ions down to 10^-6 M can be determined. Components of very high reactivity, such as Cd²⁺, Mn²⁺ or Zn²⁺, can also be determined as part of a multicomponent mixture.     

Kinetic spectrophotometric method for trace determination of thiocyanate based on its inhibitory effect

A kinetic spectrophotometric method for the determination of thiocyanate, based on its inhibitory effect on silver(I) catalyzed substitution of cyanide ion, by phenylhydrazine in hexacyanoferrate(II) is described. Thiocyanate ions form strong complexes with silver(I) catalyst which is used as the basis for its determination at trace level. The progress of reaction was monitored, spectrophotometrically, at 488 nm (λ_max of [Fe(CN)₅PhNHNH₂]^3?, complex) under the optimum reaction conditions at: 2.5 × 10^?3 M [Fe(CN)₆]^4?, 1.0 × 10^?3 M [PhNHNH₂], 8.0 × 10^?7 M [Ag⁺], pH 2.8 ± 0.02, ionic strength (μ) 0.02 M (KNO₃) and temperature 30 ± 0.1 °C. A linear relationship obtained between absorbance (measured at 488 nm at different times) and inhibitor concentration, under specified conditions, has been used for the determination of [thiocyanate] in the range of 0.8–8.0 × 10^?8 M with a detection limit of 2 × 10^?9 M. The standard deviation and percentage error have been calculated and reported with each datum. A most plausible mechanistic scheme has been proposed for the reaction. The values of equilibrium constants for complex formation between catalyst–inhibitor (K_CI), catalyst–substrate (K_s) and Michaelis–Menten constant (K_m) have been computed from the kinetic data. The influence of possible interference by major cations and anions on the determination of thiocyanate and their limits has been investigated.     

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.

     

阻抑乙基橙褪色动力学光度法测定痕量苯酚

在稀盐酸介质中,苯酚的存在对溴酸钾氧化乙基橙褪色反应有很强的抑制作用。本文利用光度法监测反应过程中乙基橙浓度的变化,并建立了苯酚-溴酸钾-乙基橙体系阻抑动力学光度法测定苯酚含量的方法。在选定条件下,方法的线性范围是0.008μg·m L-1~0.28μg·m L-1,检出限为0.00019μg·m L-1.     

阻抑甲基橙褪色动力学光度法测定痕量铁

在H2SO4介质中,痕量铁(Ⅲ)对KBrO3氧化甲基橙褪色反应有很强的抑制作用,建立了阻抑动力学光度法测定痕量铁(Ⅲ)的新方法。在选定条件下,方法的线性范围是0.0080~0.088μg/mL,检出限为3.18×10-9g/mL。     

Spectrophotometric determination of trace iron by using its catalytic effect on the N-phenylanthranilic acid-potassium periodate reaction.

The analytical features of the reaction between N-phenylanthranilic acid (PAA) and potassium periodate in acidic medium are explored with the aim of improving the catalytic kinetic determination of iron in water samples. In the presence of Fe(II, III), PAA is oxidized by potassium periodate in a formic acid medium to form a violet-colored compound. The reaction is followed spectrophotometrically by measuring the increase in the absorbance of the oxidation product at 525 nm. The variables that affected the reaction rate were investigated and the reaction conditions were established. Calibration graphs are linear in the range of concentrations 2 - 500 ng mL(-1). As low as 10(-8) mol L(-1) Fe(II, III) can be easily determined by the fixed time method. The established catalytic method was successfully applied to the determination of iron in tap water and in pharmaceutical samples.     

A new indicator reaction for a catalytic determination of silver

Microchimica Acta - Hydrolysis of hexachloroantimonate(V), catalysed by iodide, has been used as a new indicator reaction for the determination of silver in microquantities by a kinetic procedure....     

硫化镍试金富集-催化光度法测定痕量铑

在铑的硫酸配合物催化高碘酸钾氧化甲基红退色反应的基础上 ,提出了催化光度测定痕量铑的新方法。铑质量浓度在 0～ 0 .1 μg/mL范围内符合比尔定律 ,测定下限为 4× 1 0 - 3μg/mL。对于试样中质量分数为 1 6× 1 0 - 5%Rh的测定 ,RSD为 9 2 %,平均回收率为 89%。测定之前 ,痕量铑用小硫化镍试金富集分离。方法已用于原矿和尾矿中痕量铑的分析。     

Kinetic determination of traces of manganese in different materials by its catalytic effect on the methylene green-periodate reaction

The oxidation of Methylene Green by sodium periodate is a slow process. A kinetic method based on the catalytic effect of manganese(II) on this reaction in the presence of 1,10-phenanthroline as activator is described. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 620 nm. Under the optimal experimental conditions [4 x 10(-5)M Methylene Green, 0.2M acetate buffer (pH 4), 2 x 10(-3)M 1,10-phenanthroline, 2.5 x 10(-3)M sodium periodate, 35 degrees ], manganese(II) between 0.2 and 30 ng ml is determined by the tangent method. The accuracy of the method and the influence of 44 foreign ions have been studied and an equation for the kinetics of the catalysed reaction is proposed. The procedure has been applied to the determination of manganese in water, milk and beer with excellent results.     

A new catalytic reaction for determination of silver

Summary On the basis of some theoretical considerations a new catalytic reaction is proposed for determination of silver-the oxidation of sulphanilic acid with persulphate. In the presence of the catalyst, silver(I), the formation of the coloured reaction product proceeds much faster, which permits the determination of 1 ppm of the catalyst. The influence of the temperature, the acidity and 17 other ions on the reaction rate was also studied.

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Zusammenfassung Auf der Grundlage einiger theoretischer Überlegungen wurde eine neue katalytische Reaktion zur Silberbestimmung vorgeschlagen, nämlich die Oxydation der Sulfanilsäure mit Persulfat. In Gegenwart von Silber als Katalysator bildet sich das gefärbte Reaktionsprodukt viel schneller, so daß sich 1 ppm des Katalysators bestimmen läßt. Der Einfluß der Temperatur, der Acidität sowie die Wirkung von 17 anderen Ionen auf die Reaktion wurden ebenfalls untersucht.

     

阻抑二甲基黄褪色反应动力学光度法测定痕量钛

基于乳化剂OP存在下的0．08mol／L H2SO4介质中，痕量Ti(Ⅳ)对KBrO3氧化二甲基黄(DMY)的褪色反应有明显的阻押作用，建立了测定痕量钛(Ⅳ)的阻押动力学光度法，方法检出限为0．21μg/L，线性范围为0～8．0μg/L。结合溶剂萃取分离，用于人发、植物、茶叶及岩石样品中痕量钛的测定，结果与标准值相符。精密度试验以ω(Ti)为10^-6水平的试样检测，其RSD(n=6)≤3．4％。     

Kinetic-spectrophotometric determination of trace amounts of vanadium(V) based on its catalytic effect on the reaction of DBM-arsenazo and potassium bromate

A simple and sensitive kinetic-spectrophotometric method is developed for the determination of trace vanadium(V), based on the catalytic effect of vanadium(V) on the oxidation of DBM-arsenazo by potassium bromate in 0.0138 moll(-1) phosphoric acid medium and at 100 degrees C in the presence of citric acid as activator. The absorbance is measured at 528 nm with the fixed-time method. The optimization of the operating conditions regarding concentrations of the reagents, temperature and interferences are also investigated. The working curve is linear over the concentration range 0-20 ngml(-1) of vanadium(V) with good precision and accuracy and the detection limit was down to 3.44 ngl(-1). The relative standard deviation for a standard solution of 14 ngml(-1) is 0.28% (n=11). The apparent activity energies of the catalytic reaction and the non-catalytic reaction are 73.48, 113.5 kJ/mol, respectively. The proposed method proved highly sensitive, selective and relatively rapid for the assay of vanadium at low-level range of 0-20 ngml(-1) without any pre-concentration step. Thw method was applied to the determination of vanadium(V) in steels, rice, flour, cabbage, potato, fish, shrimp and tea samples with satisfactory results. The obtained results for the steel samples were excellent agreement with the standard reference values. The analytical results of the rice, flour, cabbage, potato, fish, shrimp and tea samples were excellent agreement with those of atomic absorption spectrometry. The recovery experiments have been made for the rice, flour, cabbage, potato, fish, shrimp and tea samples except the steels; excellent results were obtained. The relative standard deviations were over the range of 0.18-2.60% and the recoveries were over the range of 98.00-102.4%, respectively. The analytical results obtained were satisfactory.     

Wireless sensing determination of uranium(IV) based on its inhibitory effect on a catalytic precipitation reaction

The adsorption of Eu(III) on multiwalled carbon nanotubes (MWCNTs) as a function of pH, ionic strength and solid contents are studied by batch technique. The results indicate that the adsorption of Eu(III) on MWCNTs is strongly dependent on pH values, dependent on ionic strength at low pH values and independent of ionic strength at high pH values. Strong surface complexation and ion exchange contribute to the adsorption of Eu(III) on MWCNTs at low pH values, whereas surface complexation and surface precipitation are the main adsorption mechanism of Eu(III) on MWCNTs. The desorption of adsorbed Eu(III) from MWCNTs by adding HCl is also studied and the recycling use of MWCNTs in the removal of Eu(III) is investigated after the desorption of Eu(III) at low pH values. The results indicate that adsorbed Eu(III) can be easily desorbed from MWCNTs at low pH values, and MWCNTs can be repeatedly used to remove Eu(III) from aqueous solutions. MWCNTs are suitable material in the preconcentration and solidification of radionuclides from large volumes of aqueous solutions in nuclear waste management.     

Kinetic determination of cysteine and thiosulphate by inhibition of Hg(II) catalyzed ligand substitution reaction

The sulphur containing inhibitors (I), cysteine (Cys) and sodium thiosulphate (THS), have been found to inhibit Hg(II) catalyzed exchange of cyanide in hexacyanoferrate(II) by nitroso-R-salt (NRS). The inhibitory effect of both the ligands are attributed to their binding tendencies with Hg(II) leading to the formation of catalyst-inhibitor (C-I) complex. The reactions have been followed spectrophotometrically in aqueous medium at 720 nm by noting the increase in absorbance of the green colour product, [Fe(CN)₅NRS]³⁻ at pH 6.50 ± 0.02, temp 25.0 ± 0.1 °C and ionic strength (μ) 0.1 M (KNO₃). A most plausible mechanistic scheme involving the role of analytes (inhibitors) has been proposed. The values of equilibrium constants for complex formation between catalyst-inhibitor (K_CI), catalyst-substrate (K_S) and Mechaelis-Menton constant (K_m) have been computed from the kinetic data. The linear calibration curves have been established between absorbance and inhibitor concentrations under specified conditions. Cys and THS have been determined in the range 1-5 × 10^− 7 M and 4.9-16.9 × 10^− 7 M respectively. The detection limits have been computed to be 1 × 10^− 7 M and 4.9 × 10^− 7 M for Cys and THS, respectively.     

Kinetic thermometric determination of traces of manganese by its catalytic effect on the reaction between Tiron and hydrogen peroxide

We have developed a highly sensitive kinetic thermometric method for the determination of traces of Mn(II) by its catalytic effect on the oxidation of Tiron by hydrogen peroxide. The reaction is monitored by the initial-rate method, which is applied to temperature-time curves. Under the optimum conditions established in preliminary experiments, manganese can determined over the range 1–120 ng/mL, with an rsd of 5.8% and 1.3% for S ng/mL and 40 ng/mL Mn(II), respectively. The proposed method is subjected to few interferences, the most serious of which is posed by Pb(II), with a tolerated ratio of 201. The method was satisfactorily applied to the determination of Mn(II) in various types of sample (water, beer and wine).

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Zusammenfassung Es wurde eine hochempfindliche kinetische thermometrische Methode zur Bestimmung von Spuren an Mn(II) anhand dessen katalytischen Effektes auf die Oxidation von Tiron mit Wasserstoffperoxid entwickelt. Der Verlauf der Reaktion wurde über die Anfangsgeschwindigkeiten bei den Temperatur-Zeit-Kurven verfolgt. Unter in Vorexperimenten ermittelten optimalen Bedingungen kann Mangan im Bereich 1–120 ng/ml mit einer relativen Standardabweichnung von 5.8% bzw. 1.3% für 5 ng/ml bzw. 40 ng/ml Mn(II) bestimmt werden. Das Verfahren wird von einigen Kreuzwirkungen beeinflußt, von denen die intensivste der Einfluß von Pb(II) mit einem zulässigen Verhältnis von 201 ist. Diese Technik konnte zur Bestimmung von Mn(II) in den verschiedenartigsten Proben (Wasser, Bier, Wein) zufriedenstellend angewendet werden.

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The financial support of DGIC.I (Grant PS 89-0146) is grealfully acknowledged.     

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.     

Polarographic determination of zirconium at trace level

An indirect polarographic method has been developed for the determination of zirconium by formation of molybdozirconophosphoric acid, its extraction with MIBK or a mixture of diethyl ether and 1-butanol, stripping with alkali and measurement of the Mo(VI) by its catalytic effect on the polarographic reduction of hydrogen peroxide. Depending on the extradant, a detection limit of 2.5 or 8.9 mu/gl, can be achieved.     

偶氮胭脂红B动力学光度法测定Fe(III)

动力学光度法测定铁[1,2]多用2,4 二氯苯酚+4 氨基安替比林[3]、苄橙[4]、次甲基蓝[5]、酸性铬蓝Ｋ[6]和二溴对甲基偶氮羧[7]等为监测组分,以Ｈ2Ｏ2为氧化剂,α,α 联吡啶为活化剂。本文用催化光度法确定铁(ＩＩＩ)催化高碘酸钾氧化偶氮胭脂红Ｂ褪色反应的动力学条件及有关参数,仅以高碘酸钾为氧化剂,不使用活化剂,操作简单、快速,用于水样及生物样中铁的测定,结果满意。1　实验部分移取0 20ｍｌＦｅ(ＩＩＩ)标准工作溶液(1 0μｇ/ｍｌ)于25ｍｌ比色管中,依次加入2 0ｍｌ0 02ｍｏｌ/Ｌ硫酸溶液,1 5ｍｌ0 010ｍｏｌ/Ｌ高碘酸钾溶液,1 5ｍ…