Kinetic spectrophotometric determination of thiocyanate based on its inhibitory effect on the oxidation of methyl red by bromate.

A kinetic spectrophotometric method for measuring thiocyanate is described. The proposed method is based on the inhibitory effect of thiocyanate on the oxidation of Methyl Red by bromate in the presence of nitrite, which was monitored at 520 nm. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. Thiocyanate can be measured in the range of 0.05-1.1 microg ml(-1) with a detection limit of 0.025 microg ml(-1). This method has been used to determine trace thiocyanate in urine and tap water samples.     

煌焦油蓝-溴酸钠体系催化动力学光度法测定痕量甲醛

基于H2SO4介质中甲醛催化NaBrO3氧化煌焦油蓝的褪色反应,建立了测定痕量甲醛的催化动力学分析方法。探讨了该方法的反应机理,对其反应条件进行了研究。测定线性范围为0．16～2．00μg／mL,检出限为8ng／mL。方法已应用于海产品水发液中痕量甲醛的测定。     

溴酸钾氧化酸性铬深蓝动力学光度法测定痕量亚硝酸根

亚硝酸根是环境中重要的污染物之一,是水质、环境、食品等检测的一个重要项目。催化动力学方法测定痕量亚硝酸根已有较多的报道^[1-6],但未见利用酸性铬深蓝指示物质的报道,酸性铬深蓝是一种配位滴定的指示剂。作者发现在稀疏酸介质中,亚硝酸根对溴酸钾氧化酸性铬深蓝褪色反应有灵敏的催化作用,并研究了该指示反应的动力学条件,建立了催化光度法测定亚硝酸根的新方法。该方法灵敏、简便,可用于水、蔬菜中亚硝根的测定。     

乙基橙-溴酸钾体系动力学光度法测定痕量甲醛

研究了在稀H2SO4介质中,痕量甲醛催化KBrO3氧化乙基橙褪色反应的适宜条件和影响因素,建立了测定痕量甲醛的动力学光度法。方法采用固定时间法于507 nm波长处测量体系的吸光度,在适宜条件下,ΔA与甲醛质量浓度具有良好的线性关系,方法的线性范围为0~0.24 mg/L,检出限为0.004 mg/L。该方法用于饮料、废水和废气中痕量甲醛的测定,测定结果的相对标准偏差RSD≤3%(n=6),回收率为102%。     

KBrO3-溴酚蓝体系催化光度法测定微量甲醛

在室温及H2SO4介质中, 基于甲醛对KBrO3氧化溴酚蓝有显著的促进作用, 建立了测定微量甲醛的动力学催化光度法. 方法的线性范围为0.70～11.0 μg/mL, 检出限为0.015 μg/mL. 用该方法对某实验室废水中甲醛含量进行了测定, 结果满意.     

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.

     

Spectrophotometric determination of trace nitrite based on catalytic oxidation of thionine by potassium bromate

A kinetic method for the determination of trace nitrite (7 × 10^?9–1.2 × 10^?6 M) based on its catalytic effect on the reaction between potassium bromate and thionine in strongly acidic media is reported. The reaction is monitored spectrophotometrically by measuring the decreasing colour of thionine at 602 nm by the fixed-time method. At a given time of 5 min at 30°C, the detection limit is 2 × 10^?9 M (0.001 absorbance ratio, b = 1 cm) and the relative standard deviation for 1 × 10^?6 M nitrite is 2.6% (n = 6). The method is free from most interferences, especially from large amounts of nitrate. The procedure was successfully applied to the determination of trace nitrite in natural water and sausage samples without preconcentration and separation.     

Spectrophotometric determination of nitrite based on its catalytic effect on the oxidation of carminic acid by bromate

A highly sensitive and selective method is described for the determination of trace amounts of nitrite based on its effect on the oxidation of carminic acid with bromate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 490 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1.8×10⁻¹ mol l⁻¹ H₂SO₄, 3.8×10⁻³ mol l⁻¹ KBrO₃, and 1.2×10⁻⁴ mol l⁻¹ carminic acid at 30°C. By using the recommended procedure, the calibration graph was linear from 0.2 to 14 ng ml⁻¹ of nitrite; the detection limit was 0.04 ng ml⁻¹; the R.S.D. for six replicate determinations of 6 ng ml⁻¹ was 1.7%. The method is mostly free from interference, especially from large amounts of nitrate and ammonium ions. The proposed method was applied to the determination of nitrite in rain and river water.     

Flotation—spectrophotometric determination of osmium with thiocyanate and methylene blue

A sensitive flotation—spectrophotometric method, based on the ion associate formed by the anionic thiocyanate complex of osmium with the basic dye methylene blue (MB) is described. The ion associate precipitates when the aqueous solution is shaken with toluene, and the separated and washed compound is dissolved in acetone. The molar absorptivity is 2.2 × 10⁵ l mol^-1 cm^-1 at 655 nm. Beer's law is obeyed. The molar ratio of Os:SCN:MB in the separated and washed ion associate is 1:6:3. Ruthenium reacts similarly. The method is applied to the determination of traces of osmium in crucible platinum after separation of osmium by distillation as tetroxide.     

Flow injection determination of formaldehyde by its catalytic effect on the oxidation of sulfonazo III by bromate with spectrophotometric detection.

A simple and sensitive flow injection method with spectrophotometric detection was developed for the determination of formaldehyde. The method is based on the catalytic effect of formaldehyde on the oxidation of sulfonazo III with bromate in acidic media. The decrease in absorbance of the reaction mixture was measured at 566 nm. The calibration graph was linear in the range of 0.005 to 2.80 microg ml(-1) formaldehyde at a rate of 38 +/- 4 samples h(-1). The limit of detection was 4 ng ml(-1). The relative standard deviations for ten replicate measurements of 0.20, 0.50 and 1.00 microg ml(-1) formaldehyde were 1.3, 0.8 and 0.7%, respectively. The method was applied to the determination of formaldehyde in river water, shampoo and melamine-formaldehyde resin.     

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.     

KBrO3氧化甲基紫褪色动力学光度法测定食品中痕量钒

基于0.004 mol/L的柠檬酸介质中,痕量V(Ⅴ)催化KBrO3氧化甲基紫的褪色反应,建立了测定痕量V(Ⅴ)的动力学光度法。方法的检出限为1.23μg/L,线性范围为0～0.16μg/mL。讨论了酸度、反应物浓度、温度、反应时间、干扰离子等因素的影响,确定了该体系反应的最佳条件。在25 mL溶液中,测定2.0μg V(Ⅴ)的RSD为1.9%(n=11)。方法可用于测定小麦和苹果中的痕量V(Ⅴ),RSD为1.1%～2.7%,标准加入回收率为97.6%～99.0%。     

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.     

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…     

Spectrophotometric reaction rate method for the determination of osmium by its catalytic effect on the oxidation of gallocyanine by bromate

A simple kinetic spectrophotometric method was developed for the determination of osmium. The method is based on the catalytic effect of osmium as osmium tetroxide on the oxidation of gallocyanine by bromate at pH 7. The reaction is monitored spectrophotometrically by measuring the decreasing absorbance of gallocyanine at 620 nm by the fixed-time method. A detection limit of 0.01 ng/ml and linear calibration curve from 0.1 to 100 and from 100 to 1200 ng/ml Os(VIII) is reported. The relative standard deviation for 0.0100 microg/ml Os(VIII) is 0.8% (N = 10). The method is free from most interferences. Osmium in synthetic samples is determined by this method, with satisfactory results.     

Kinetic-spectrophotometric determination of traces of vanadium(V) by its catalytic effect on the oxidation of 1,4-dihydroxyphthalimide dioxime with bromate

A kinetic-spectrophotometric method for the determination of trace amounts of vanadium(V) is described. It is based on the catalytic action of this ion on the oxidation of 1,4-dihydroxyphthalimide dioxime by bromate, which yields a red-violet product in acidic medium. The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 500 nm and 30°C. Using several kinetic methods (tangent, fixed-time and fixed-absorbance), vanadium(V) in the range 10–400 ng ml^?1 can be determined. The proposed methods are hardly subject to interferences. The tangent method was used for the determination of vanadium in atmospheric particulate matter, human serum and synthetic mixtures. The kinetic parameters of the catalysed and uncatalysed reactions are reported.     

Kinetic spectrophotometric determination of rutin by its inhibitory effect on the oxidation of amaranth by potassium periodate

A novel kinetic spectrophotometric method is described for the determination of rutin. The method is based on the inhibitory effect of rutin on the oxidation reaction of amaranth by potassium periodate in acidic media at 100 degrees C. The linear range for the determination of rutin is 0.02 - 0.50 microg/ml, and the detection limit is 0.014 microg/ml. The method has been successfully applied to the determination of rutin in medicine of rutin tablet and traditional Chinese medicine.     

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-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.     

Kinetic spectrophotometric method for the determination of oxalic acid by its catalytic effect on the oxidation of safranine by dichromate

A new catalytic kinetic spectrophotometric method for the determination of oxalic acid has been described based on its catalytic effect on the redox reaction between safranine and dichromate in dilute sulfuric acid media. The reaction is monitored photometrically by measuring the decrease in absorbance of safranine at the maximum wavelength of 530 nm. Under the optimum conditions, a calibration graph from 0.10 to 10.00 microg ml(-1) of oxalic acid with a detection limit of 0.08 microg ml(-1) was obtained. The relative standard deviation (R.S.D.) for ten replicate measurements of 1.0 and 5.0 microg ml(-1) oxalic acid was 2.7 and 2.5%, respectively. The purposed method is simple, sensitive, selective and inexpensive. The applicability of the proposed method was determined by the determination of oxalic acid in spinach and wastewater samples with satisfactory results.