Highly selective spectrophotometric flow-injection determination of trace amounts of bromide by catalytic effect on the oxidation of m-cresolsulfonephthalein by periodate

A new flow-injection method is reported for the determination of bromide. The method is based on catalytic effect of bromide on the oxidation of m-cresolsulfonephthalein by periodate in acidic media. The reaction was followed spectrophotometrically by measuring the decrease in absorbance at 528 nm. The influence of pH, reagent concentration and manifold variables on the sensitivity was studied. Under optimum conditions, a calibration graph was obtained in the range of 0.160-20.00 microg ml(-1) bromides with a limit of detection of 0.150 microg ml(-1) bromide. The relative standard deviation for ten replicate measurement of 1.0 microg ml(-1) bromide was 2.1%. The influence of potential interfering ions on the selectivity was studied. The method successes to measure bromide in the presence of other halide ions. The method was used to measure bromide in river water and tap water.     

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…     

A selective catalytic colorimetric determination of manganese in subnanogram amounts through oxidation of sulphanilic acid by potassium periodate with 1,10-phenanthroline as activator

Summary The catalytic oxidation of sulphanilic acid by potassium periodate with manganese(II) as catalyst has been studied with 1,10-phenanthroline as an activator. The activator takes part in the formation of mixed complexes with the catalyst and the reagents, which favours contact and electron transfer between the latter. By this mechanism, 1,10-phenanthroline lowers the detection limit of the reaction by more than two orders of magnitude and increases its selectivity. On the basis of the investigations made, a catalytic method with low detection limit (0.5 ng/ml) and good reproducibility (coefficient of variation 2.6%) for the determination of manganese(II) in pure solutions has been developed.     

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.     

高碘酸钾氧化丽春红-2R催化动力学单扫描示波极谱法测定痕量Fe(Ⅲ)的研究

研究了在H2SO4介质中,痕量Fe(Ⅲ)催化KIO4氧化丽春红-2R的褪色反应,提出了催化动力学单扫描示波极谱法测定痕量铁的新方法。在1.6×10-3mol/LH2SO4介质中,丽春红-2R在汞电极上产生1个灵敏的还原峰,峰电位为-0.224V(vs.SCE)左右;在KIO4存在下,丽春红-2R峰电流的降低与加入Fe(Ⅲ)质量浓度在0~0.04μg/mL范围内呈良好的线性关系,检出限达到6.28×10-9μg/mL。同时探讨了反应条件、极谱波的性质和电极反应机理,已用于中草药中铁的测定,回收率为98.9%~102.2%。     

Rapid determination of microorganisms using a flow-injection system

An automated method for the rapid determination of microorganisms using a flow-injection system is presented. Electrochemical measurement of a mediator reduced by microbial metabolism allowed the determination of fungi and bacteria in a few minutes. The lowest detection limit was 5 × 10⁶ colony-forming units (cfu) ml^?1 for Escherichia coli. Correlation between the flow-injection method and standard microbiological methods was excellent (r = 0.997, n = 4 for Beauveria bassiana; r = 0.997, n = 7 for E. coli). The flow-injection system was applied to the on-line control of an E. coli cultivation.     

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....     

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.     

Differential catalytic determination of iridium(IV) and rhodium(III) based on the oxidation of N-methyldiphenylamine-4-sulfonic acid

The kinetics of the oxidation of N-methyldiphenylamine-4-sulfonic acid with periodate ions was studied in weakly acidic solutions in the presence of iridium(IV), rhodium(III), and their mixtures. Oxidation rate constants were determined in the presence of individual catalysts and their mixtures. The synergetic effect of iridium(IV) and rhodium(III) on the rate of the indicator reaction was estimated; the range of catalyst ratios for the simultaneous determination of analytes was determined. The effect of some factors (oxidant nature and concentration, temperature, the ionic strength of solution, and interfering ions) on the rate of the indicator reaction in the presence of iridium(IV) and rhodium(III) mixtures was assessed. A procedure for the differential catalytic determination of iridium(IV) and rhodium(III) was proposed and tested in the analysis of artificial mixtures and a platinum concentrate of complex composition (KP-5).     

An unusual case of activation in homogeneous catalytic analytical reactions: 1,10-phenanthroline as an activator of the catalytic action of Mn(II) on the oxidation ofp-phenetidine by potassium periodate

Summary A case of co-ordinatively saturated and unsaturated activatorcatalyst complexes being active has been observed for the first time in the field of activated catalytic analytical reactions with Mn(II)-catalysedp-phenetidine oxidation by periodate, with 1,10-phenanthroline as activator. An analytical procedure for determining trace amounts of Mn(II) has been developed on the basis of this catalytic reaction. The new method has better analytical characteristics than the one using no activator.

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Ein Fall von Aktivierung homogen katalysierter analytischer Reaktionen. 1,10-Phenathrolin als Aktivator der katalytischen Wirkung von Mn(II) bei der Oxydation von p-Phenetidin durch Kaliumperjodat

Zusammenfassung Aktivierung durch koordinativ gesättigte und ungesättigte Aktivator-Katalysator-Komplexe wurde erstmals auf dem Gebiet analytischer Reaktionen bei der Mn(II)-katalysierten Oxydation von p-Phenetidin durch Perjodat festgestellt, wobei 1,10-Phenanthrolin als Aktivator fungiert. Ein analytisches Verfahren zur Bestimmung von Mn(II)-Spuren wurde auf dieser Basis entwickelt. Es erwies sich als besser als das Verfahren ohne Aktivator.

     

Simultaneous determination of formaldehyde and methanol by flow-injection catalytic spectrophotometry

A flow-injection method is proposed for the simultaneous catalytic determination of formaldehyde and methanol on the basis of the catalytic action of formaldehyde upon the redox reaction between crystal violet and potassium bromate in a phosphoric acid medium and on-line oxidization of methanol into formaldehyde using a lead dioxide solid-phase reactor. The indicator reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of crystal violet at the maximum absorption wavelength of 610 nm. A technique based on three sampling loops with a single injection valve is developed. The flow-injection system produces a signal of main peak with two shoulders of the same height. The height of the shoulders corresponds to the formaldehyde concentration, and the height difference between the shoulders and the main peak corresponds to the methanol concentration. The detection limit is 0.1 μg/mL for formaldehyde and 1.0 μg/mL for methanol with the sampling rate of 10 samples per hour. The relative standard deviations for 11 replicate determinations of formaldehyde (1.0 μg/mL) and methanol (10 μg/mL) are 1.1 and 2.1%, respectively. The method has been successfully applied to the simultaneous determination of formaldehyde and methanol in some gas samples. The text was submitted by the authors in English.     

Kinetic, spectrophotometric determination of nanogram levels of manganese(II) using catalytic azo dye—potassium periodate—1,10-phenanthroline system

The catalytic effect of manganese(II) on the oxidation of the dye, sodium salt of 4-(2-hydroxynaphth-1-ylazo)benzenesulfonic acid, with potassium periodate in the presence of 1,10-phenanthroline in weakly acidic media was studied. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the dye at λ = 483 nm. Under the optimum conditions Mn(II) concentration within the range of 0.08–4 ng cm⁻³ could be determined by the fixed-time method with a detection limit of 0.025 ng cm⁻³. The method was applied for the determination of manganese content in tomatoes, aubergine, white radish, and French beans. The results showed a good agreement with those obtained by atomic absorption spectrophotometry.     

Substoichiometric determination of iridium using PAN as a reagent

Conditions are established for the substoichiometric determination of iridium employing 1-/2-pyridylyzo/-2-naphthol /PAN/ as a chelating agent. Iridium forms a red coloured complex /12/ with PAN at pH 5 /acetate buffer/, on heating for 60 min in a boiling water bath. The complex was extracted with chloform. Tens of micrograms of iridium were determined with an accuracy of ±0.38%. Effects of diverse metal ions on the determination of iridium were studied and methods for suppression of interferences were developed.     

The determination of traces of iridium in rhodium by neutron activation analysis

Iridium traces were determined in rhodium by thermal neutron activation for 2 days at a flux of 4.10¹¹ n·cm^-2·sec^-1. After cooling for at least 1 week, the samples were analysed by γ-spectrometry. No radiochemical separations were required. Special attention was paid to self-absorption phenomena in the rhodium samples.     

Studies on iridium and platinum determination in metallic rhodium by NAA and CPAA

The determination of Ir and Pt in rhodium neutron monitors was investigated via¹⁹²Ir and¹⁹⁹Au after neutron activation, via¹⁹¹Pt and¹⁹⁴Au–¹⁹⁶Au after proton activation. Ir was determined by instrumental NAA. A chemical separation of gold, with a yield measurement method by a radioactive tracer, was developed for platinum determination after neutron or proton irradiation.     

Diphenylcarbazone as an internal indicator in mercurimetric analysis: The determination of cerium by potassium thiocyanate

Summary The quantitative oxidation of thiocyanate by ceric sulphate has been studied and the method utilised for the determination of small quantities of cerium by back titrating the excess (unreacted) KSCN against standard mercuric nitrate with diphenylcarbazone as the internal indicator. Accurate results are obtained under the specified experimental conditions and the procedure is more simple and direct than that adopted during earlier studies of the above redox reaction.Grateful thanks of the author are due to Professor S. S. Joshi for facilities during the work and to the National Institute of Sciences of India for award of a Research Fellowship.     

Radical polymerization as an indicator reaction for determination of organic compounds

Polymerization of methyl methacrylate (MMA) and 4-vinylpyridine (VP) has been carried out in an aqueous solution in the presence of the initiating system persulfate-tetramethylethylenediamine. The reaction rate has been monitored by measuring the light absorbance of the suspension of the resulting polymer. The effect of 26 model organic compounds on the polymerization rate has been studied. It has been shown that the VP polymerization is inhibited by a smaller number compounds (9 compounds) than the MMA polymerization (22 compounds), which indicates that the former reaction has better selectivity, whereas the determination of model compounds using the MMA polymerization reaction is more sensitive. This is explained by the lower chain growth rate constant for VP vs. MMA and different stationary concentrations of radicals in the systems. The use of these indicator polymerization reactions makes it possible to distinguish some closely related compounds, e.g., 1,4-benzoquinone and 9,10-anthraquinone (MMA reaction) or dinitrophenol and 4-nitrophenol or phenol (VP reaction). Determination of ascorbic acid in a pharmaceutical formulation has been carried out.