Determination of ultratrace amounts of ruthenium(III) by the delayed autocatalytic reaction using citric acid.

A method for determination of ultratrace amounts (ppq levels) of ruthenium(III) was developed using a copper(II)-phthalocyanine-3,4',4",4"'-tetrasulfonic sodium salt (Cu-PTS) as an indicator in a potassium bromate autocatalytic reaction system. A satisfactory calibration curve of ruthenium(III) ion was obtained by the time measurement in the concentration range of 1 x 10(-13) M to 5 x 10(-12) M with the relative standard deviation (RSD) of 2.8% (n=5). The determination limits (3sigma) were 3.30 x 10(-14) M (3.34 ppq).     

溴酸钾-鲁米诺后化学发光法检测水中微量偏二甲肼

实验发现偏二甲肼(UDMH)在溴酸钾-鲁米诺化学发光反应体系中的后化学发光反应.在对这一后化学发光反应的动力学性质、发光条件,包括溴酸钾浓度、鲁米诺浓度、管长、流速和酸碱度条件等研究的基础上,建立了后化学发光反应法测定偏二甲肼的新方法,并讨论了其可能的反应机理.该方法的线性范围为1.0×10-7～1.0×10-5g/L...     

The use of 2,6-dichlorophenol-indophenol as indicator in iodometric titrations with ascorbic acid

2,6-Dichlorophenol-indophenol can be used as an indicator in iodometric methods, provided that near the end-point the solutions can be buffered with potassium hydrogen carbonate, so that ascorbic acid can be used as the titrant. Procedures for the determination of iodine, chlorine, bromine, hypochlorite, Chloramine T, bromate, iodate, permanganate, dichromate, copper(II), hydrogen peroxide, peroxydisulphate, thiosulphate, sulphite, sulphide, hydrazine and formaldehyde are described.     

A Novel Chemical Oscillator with Tyrosine as the Substrate

A new chemical oscillating reaction system involving the manganese(Ⅱ)-catalyzed reaction among potassium bromate, acetone and tyrosine in acidic medium was described in this paper. The apparent activation energy of the induction period (Ein) and that of oscillation period (Ep) were calculated, Ein=110.61KJ/mol, Ep=159.41KJ/mol. The optimum concentration of each reactant was investigated and a steady chemical oscillating system was obtained.     

C.I.颜料红177中间体的制备工艺改进

本文较为系统地研究了铜粉催化剂加入方式对C.I.颜料红177中间体4,4'-二氨基-1,1'-二蒽醌-3,3'-二磺酸(DAS)合成过程中的乌尔曼偶联反应速率的影响规律。 研究结果表明,在55 ℃较佳反应温度下,先加入与溴氨酸钠质量比为2:5的铜粉,反应一段时间后再加入与溴氨酸钠的质量比为1:5的铜粉,与一次性加入与溴氨酸钠的质量比为3:5的铜粉相比较,综合反应时间可节省2~3 h。 另外,对于DAS中混有的铜盐,采取在制备过程中加入柠檬酸的方法予以去除,此举可提高DAS的纯度。 当铜粉与柠檬酸的质量比为6:1时,可使DAS中铜盐的含量小于0.001%。 此外还探究了蒸馏后滤液的剩余量对DAS收率的影响,结果表明,滤液的剩余量在20 mL时,DAS的收率在95%以上。 基于本文的研究结果提出,欲进一步提高该反应的收率,需要寻找更高效的催化剂。     

Flow-Injection Determination of Iron Based on Its Catalysis on the Oxidation Reaction of Xylenol Orange by Potassium Bromate

A flow injection system is proposed for catalytic kinetic spectrophotometric determination of trace iron(II + III). The involved reaction is based on the catalytic effect of iron(III) on oxidation reaction of xylenol orange by potassium bromate to form a blue-violet complex. Iron(II) is also determined, being oxidized to iron(III) by potassium bromate. The calibration graph is linear in the range of 0.02–10.0 µg l^?1 and 10.0–1100 µg l^?1. The relative standard deviation is 1.5% for 4.0 µg l^?1 iron(III) and 2.3% for 60.0µg l^?1 iron(III) (n = 11). The presented system was applied successfully to the determination of iron in natural waters.     

KBrO_3-邻氨基酚体系催化动力学光度法测定微量Cu(Ⅱ)

在pH为4.5的HAc-NaAc缓冲溶液介质中,Cu(Ⅱ)能催化KBrO_3氧化邻氨基酚而显色,据此建立了测定微量Cu(Ⅱ)的新方法。方法的测定波长为430nm,反应温度为60℃时控制反应时间为6min,Cu(Ⅱ)在0.10~1.2μg/mL范围内吸光度与Cu(Ⅱ)的浓度呈良好的线性关系,相关系数r为0.9971。方法用于测定冶炼厂电解银废液中铜含量,相对标准偏差为2.49%(n=6),加标回收率在91.6%~99.4%之间。     

Catalytic activity of noble metal ions for the degradation of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine in the presence of oxidizing agent, and its application to the determination of ultra trace amounts of ruthenium

Trace quantities of ruthenium(II) ion catalyze the oxidation of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine (TPPS) by potassium bromate. This reaction can be used for the determination of ultra trace amounts of ruthenium using the water-soluble porphyrin with its high molar absorbance. The scope of the reaction was investigated in terms of the reaction conditions and selectivity with respect to other noble metal ions. The effect of pH, concentration of bromate, the reaction time, and the type of metalloporphyrin were studied so as to optimize the method for the determination of trace amounts of Ru(III). The apparent reaction rate constant for the disappearance of TPPS (or metal-TPPS) is proportional to the root of the concentration of bromate, and directly related to that of Ru(III). The limit of detection is 0.11?nM (equal to 10.7?pg?mL^?1) at pH?4.25, where the turnover number is 201. The reproducibility for five measurements at 2.7?nM of Ru(III) was 2.9%.

Molten lithium nitrate-potassium nitrate eutectic: some reactions of copper(II) and of metallic silver

Copper(II) nitrate trihydrate has been successfully dehydrated in lithium nitrate-potassium nitrate eutectic at 140°C. At 300°C it commenced reaction as a Lux-Flood acid precipitating copper(II) oxide. With potassium iodide it reacted at 140°C to form copper(I) iodide and iodine but at 180°C the insoluble product was a mixture of copper(I) iodide and copper(II) oxide. With powdered silver a violent reaction occurred at 160°C, yielding silver(I) cations, nitrogen dioxide and copper(II) oxide. The stoichiometries of these reactions have been established and some reaction pathways suggested. Metallic silver was found to react to a much larger extent with a Lux-Flood acid (pyrosulphate) in solution than with nitrogen dioxide giving support to the nitryl cation as the acidic species in nitrate melts.     

柱后衍生离子色谱法同时测定瓶装水中的碘酸根、亚氯酸根和溴酸根

水中的碘酸根、亚氯酸根和溴酸根是重要的消毒副产物,主要通过大体积浓缩后直接电导检测,或通过柱前或柱后化学反应将目标物转化成容易检测的物质后检测。本方法采用大体积进样柱后衍生紫外检测的分析方法,通过条件优化获得了较高的灵敏度和信噪比。利用一套自动分析系统,可以满足饮用水中痕量碘酸根、亚氯酸根、溴酸根的同时监测。碘酸根、亚氯酸根和溴酸根的检出限分别为0.5,0.4,0.1 μg/L。对于不同的加标样品,碘酸根、亚氯酸根和溴酸根的回收率分别为70.8%~98.0%,92.4%~100%和93.2%~104.1%。该方法应用于北京市场上的瓶装饮用水分析,结果显示瓶装纯净水中的碘酸根、亚氯酸根、溴酸根浓度均低于检出限,而瓶装矿泉水中碘酸根、溴酸根的最高含量分别达到9.4 μg/L和78.4 μg/L。     

Highly Sensitive and Selective Determination of Manganese in Tea Leaves by a Catalytic Kinetic Spectrophotometric Method

The catalytic effect of manganese(II) on the oxidation of barium diphenylamine sulfonate (BDAS) with potassium bromate in sulfuric acid was studied. Progress of the reaction was monitored, spectrophotometrically, by measuring absorbance changes at 547.5 nm. A highly sensitive, selective and simple method was accordingly developed for the determination of trace amounts of Mn(II), with no need for a separation or pre‐concentration step. Effects of reaction time, concentration of reagents, temperature and ionic strength on the reaction rate were studied. In the optimized conditions, manganese could be determined in a range of 1 to 60 ng mL^?1 with a detection limit of 0.2 ng mL^?1. The proposed method was successfully applied to the determination of manganese in tea leaves.     

Copper(II)-catalyzed ether synthesis from aliphatic alcohols and potassium organotrifluoroborate salts

[reaction: see text] A protocol for the copper(II)-catalyzed etherification of aliphatic alcohols under mild and essentially neutral conditions is described. Air- and moisture-stable potassium alkenyl- and aryltrifluoroborate salts undergo cross-coupling with a variety of aliphatic primary and secondary alcohols and phenols, and are tolerant of a range of functional groups. The optimized conditions utilize catalytic copper(II) acetate with 4-(dimethylamino)pyridine as ligand in the presence of 4 A molecular sieves under an atmosphere of oxygen.     

The application of the ph-stat method to metal ion-catalyzed reactions

The pH-stat method, which is well known in organic chemistry and biochemistry, is used for the kinetic determination of metal ion catalysts. Indicator reactions that involve protons can be followed by controlled addition of standard base or acid. This is illustrated by the following examples: determination of copper(II) (0.03–0.3 μg ml^-1) with the indicator reaction ascorbic acid—peroxydisulphate; determination of molybdenum(VI) (0.2–2.5 μg ml^-1) with the indicator reaction thiosulphate—hydrogen peroxide; determination of zirconium(IV) (0.2–2 μg ml^-1) with the indicator reaction iodide—hydrogen peroxide; and determination of vanadium(V) (0.2–2 μg ml^-1) with the indicator reaction iodide—bromate. For one example, the copper—ascorbic acid—peroxydisulphate reaction, it is shown that the pH-stat method has distinct advantages over closed systems, giving considerably better sensitivity for the determination of copper (0.5–5 ng ml^-1 ).     

The oxidation of 3,3′-dimethoxy benzidine with potassium bromate in acidic solutions

The kinetics and mechanism of the oxidation of 3,3′-dimethoxybenzidine (oda, o-dianisidine) by potassium bromate in aqueous acidic medium were studied by monitoring the formation rate of the reaction product, 3,3′-dimethoxy 4,4′-diphenoquinone at 447 nm. The reaction is, first order with respect to both the substrate and oxidant, and second order with respect to H⁺. The oda: bromate stoichiometric ratio is 1:1. Plausible mechanism and rate laws are proposed accounting the experimental findings. Computer simulations were done using the proposed mechanism.     

Precipitation of lead as lead sulphate by destructive oxidation of EDTA

Gravimetric determination of lead (5–100 mg) by homogeneous precipitation of lead sulphate from a solution containing lead(II), EDTA and sulphate by destructive oxidation of EDTA with hydrogen peroxide or sodium bromate is described. Aluminium(III), iron(III), zinc(II), manganese(II), copper(II), nickel(II), tin(II) and antimony(III) do not interfere in the method. The method can successfully be applied to the analysis of type metal.     

Bromometric determination of carbimazole

Direct bromometric titration of carbimazole using N-bromosuccinimide (NBS) in the presence of methyl red as indicator and three indirect titrations using NBS, potassium bromate and dibromohydantoin (DBH) are developed. The direct procedure can be adopted for quantities of carbimazole ranging from 2-12 mg with mean accuracies of 100.2 +/- 0.5. The indirect procedures can be used for quantities of the drug ranging from 1-6 mg using NBS and DBH and 2-16 mg using potassium bromate with mean accuracies of 100.11 +/- 0.3, 100.49 +/- 0.31 and 100.26 +/- 0.51 respectively. The proposed procedures have been successfully applied for the analysis of the drug in tablet form and their validity has been checked using the standard addition technique. The reaction products were separated by TLC methods and their structure was elucidated using IR and NMR spectroscopy. The stoichiometry and the possible pathways of the reaction were postulated and presented.     

Potentiometric determination of bromate using an Fe(III)-Fe(II) potential buffer by circulatory flow-injection analysis.

A method for the potentiometric determination of bromate by circulatory flow injection analysis (CFIA) is described. The procedure involves the use of an Fe(III)-Fe(II) potential buffer solution, which is recycled via a reservoir. The analytical method is based on a linear relationship between the concentration of bromate and a very transient potential change in the electrode potential due to the generation of intermediate bromine during the reaction of bromate with the Fe(III)-Fe(II) potential buffer solution, which also contains NaBr, (NH4)6Mo7O24 and H2SO4. An aliquot (5 microl) of a bromate sample solution was injected into the stream of the potential buffer solution, 100 ml of which was circulated at a flow rate of 1 ml/min; the potential buffer solution stream was then returned to the reservoir after passing through a flow-through redox electrode detector. A potential change due to the reaction of the injected sample with the potential buffer in a reaction coil was measured with the detector in the form of a peak signal. The effects of the bromide, sulfuric acid and Fe(III)-Fe(II) concentrations in the potential buffer, and length of the reaction coil on the peak heights were examined in order to optimize the proposed CFIA method. The analytical sensitivities to bromate were 5.6 mV/microM for 1 x 10(-2) M and 30.9 mV/microM for 1 x 10(-3) M in the concentration of Fe(III)-Fe(II) in a potential buffer solution containing 0.35 M NaBr, 0.2% (NH4)6Mo7O24 and 1 M H2SO4. The detection limit of bromate obtained by a 1 x 10(-3) M Fe(III)-Fe(II) potential buffer solution was 0.02 microM (2.5 ppb). The numbers of repetitive determinations in which the relative sensitivities within 5% were regarded as being tolerated were ca. 4000 and 2000 for the use of only 100 ml of 1 x 10(-2) M and 1 x 10(-3) M Fe(III)-Fe(II) potential buffer solution, respectively.     

Molten lithium carbonate—sodium carbonate—potassium carbonate eutectic: The reaction of six first row transition metal cations

The reactions of manganese(II), iron(II), iron(III), cobalt(II), nickel(II) and copper(II) chlorides with the molten alkali metal carbonate eutectic have been studied by thermogravimetry. The insoluble products (binary or ternary metal oxides) have been identified by X-ray diffraction and reaction stoichiometries are suggested. Nickel(II) solutions were sufficiently stable for electronic spectroscopy and indicated, as did thermogravimetry, that addition of potassium chloride did not cause significant formation of chloro complexes.     

Liquid-liquid extraction of arsenic(III) with diluted tributyl phosphate

A 40% tributyl phosphate solution in xylene was used for the quantitative extraction of arsenic(III) from 4M hydrochloric acid/2M lithium chloride. It was stripped from the organic phase with water and determined volumetrically with potassium bromate. The period of equilibration was 3 min. Arsenic was extracted in presence of copper, cobalt, nickel, tin, bismuth, iron, cadmium and other elements which are usually associated with it in sulphide minerals and alloys.     

Determination of nitric oxide by bromate oxidation of the nitrosyl ethylenediaminetetra-acetatoiron(II) complex

A new spectrophotometric method for nitric oxide is proposed, based on formation of the nitrosyl-ethylenediaminetetra-acetatoiron(II) complex [Fe(II)NO-edta] by absorption of NO in Fe(II)edta solution and spectrophotometric determination of the NO(-)(2) produced by oxidation of the Fe(II)NO-edta complex by potassium bromate. The oxidation is easily performed completely and the absorption efficiency for 10.1-102.0 ppm NO (flow-rate, 100 ml/min) is nearly 100%. The detection limit is about 3 ppm for a sampling absorption time of 30 min.