Novel photolytic decomposition method of organic compounds with a high output low-pressure mercury lamp for voltammetric trace metal analysis

A high output low-pressure mercury lamp, 400 W L-Hg, was successfully used for the photolytic decomposition of dissolved oganic compounds as the pretreatment for the determination of trace metal ion in aqueous solution by stripping voltammetry. Various amino acids, showing interferences on voltammetric determination of metal ions, can be removed quite easily by intensive UV irradiation at room temperature. Effect of pH, concentration of electrolyte and dissolved oxygen on the efficiency of photolysis are also described. This method uses no additional chemicals such as acids or oxidants and can be carried out in closed clean conditions. Received: 1 February 1999 / Revised: 19 April 1999 / Accepted: 5 May 1999     

Application of resonance Raman spectrometry to the determination of vitamin B12.

A gel filtration technique is described for the study of the complexation of dissolved metals by humic and fulvic acids. Measurements can be made under realistic conditions of pH and free metal ion concentrations, both of which can be maintained by the use of TRIS as a buffer. The procedure permits the determination not only of the overall stability constant, but of the binding stoichiometries and the intrinsic stability constants associated with the various types of metal binding sites. The procedure has been applied to the investigation of the interaction of fresh-water fulvic acids with Cu, Zn and Ni, and has provided evidence for the existence of two different types of binding sites in the fulvic acid molecule.     

Acid–Base Titration: Analysis of Phosphoric Acid Anodizing Solutions. A Problem-Based Learning Approach

Phosphoric acid anodizing solutions are routinely titrated to monitor their concentrations; however, after successive anodizations of aluminum metal, increasing amounts of dissolved aluminum interfere with the neutralization titration. The true concentration of phosphoric acid is determined by a correction factor based on the concentration of the dissolved aluminum, which is determined industrially by flame atomic absorption spectrometry. The academic determination of a correction factor for aluminum as well as copper can be designed as a traditional or a problem-based learning exercise.     

Microtitrimetric and photometric determination of sulphur in metals in the low μg g-1 range after wet or dry evolution of hydrogen sulphide

Wet and dry techniques have been optimized for the separation of sulphur traces from metals (e.g. Ag, Cu, Cu alloys, Pb, Sn, Fe) as hydrogen sulphide, in combination with a final microtitrimetric or spectrophotomefcric determination. The metal sample can be dissolved in a mixture of hydroiodic, formic and hypophosphorous acids, and the evolved hydrogen sulphide swept with nitrogen into an absorption vessel. Alternatively, in the hydrogenation technique, the metal sample is heated in a stream of pure hydrogen up to ?1150°C and the hydrogen sulphide produced is absorbed in sodium hydroxide solution or cadmium hydroxide suspension. The sulphide is determined in the absorption vessel by microtitration with cadmium(II) titrant and dithizone as indicator. The methylene blue colour reaction is applied for the speetrophotometric determination. Precautions are taken to avoid systematic errors (losses by absorption, contamination by laboratory air) and to lower reagent blanks, so that concentrations as low as ?0.2 μg g^-1 (sample weight ?1 g) can be determined. The coefficients of variations are ?10% and 2.5% at concentration ranges of 1–10 μg g^-1 and > 10 μg g^-1, respectively.     

On-line electrolytic dissolution of solid metal samples and determination of copper in aluminium alloys by flame atomic absorption spectrometry

A flow-injection system was developed in which alloy metal samples are electrolytically dissolved and the dissolved samples are analysed by flame atomic absorption spectrometry (FAAS). The effects of electrolyte composition and electrolysis parameters on the dissolution of the sample were studied. The method was used for the determination of copper in aluminium alloys. Electrolyte solutions consisting of 0.2–1.0 M nitric acid are better than other electrolytes tested with regard to both alloy sample dissolution and determination of copper by FAAS. The peak height increases linearly with the electrolysis time or current within a certain range. The detection limit depends on the sensitivity of the detector used, and can be improved by increasing the electrolysis time or current. Generally, aluminium alloys containing 0.5–10% copper can give suitable signals for FAAS determination. The reproducibility of electrolysis and determination is about 4% for the same sampling points and 5% for different sampling points on the alloy sample.     

Metal chelate exchange in the organic phase-I Theory: application in spectrophotometry and complex chemistry

Metal chelates, extracted from an aqueous phase by organic solvents, can react with other chelating agents (or their metal chelates) dissolved in the same solvent. This exchange of metal chelates in the organic phase can be used for (1) investigation of the exchange equilibrium and composition of the metal chelates formed, (2) determination of the extraction constants, (3) preparation of new inner-complexes soluble in organic solvents, and (4) spectrophotometric determination of small amounts of metals. The theory and experimental verification of this phenomenon are given. The extraction constants of silver and zinc diethyldithiocarbamates in carbon tetrachloride have been determined by means of the extraction constants of the corresponding dithizonates. A mixed complex of arsenic(III) with dithizone and diethyldithiocarbamic acid has been prepared and its properties studied. A simple method for spectrophotometric determination of microgram quantities of arsenic is proposed.     

Second-Derivative Spectrophotometric Determination of Trace Copper after Preconcentration with the Ion Pair of 2-Nitroso-1-Naphthol-4-Sulfonic Acid and Tetradecyldimethylbenzylammonium Chloride on Microcrystalline Naphthalene or a Column

Copper is quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid and tetradecyldimethylbenzylammonium chloride on microcrystalline naphthalene in the pH range 7.1–10.7 from large volumes of aqueous solutions of various samples. After filtration, the solid mass consisting of a copper complex and naphthalene is dissolved with 5 mL of dimethylformamide, and the metal is determined by second-derivative spectrophotometry. The copper complex can alternatively be quantitatively adsorbed on tetradecyldimethylbenzylammonium–naphthalene adsorbent packed in a column and determined similarly. About 1.5 g of copper can be concentrated in a column from 300 mL of aqueous sample, where its concentration is as low as 5 ng/mL. The effects of pH, the volume of the aqueous phase, and interferences from a number of metal ions on the determination of copper have been studied in detail to optimize the conditions for its determination in standard alloys and biological samples.     

Determination of zirconium in zirconium metal and zirconium powder by use of mandelic acid

An accurate gravimetric method is proposed for the determination of zirconium in zirconium metal and zirconium powder by use of mandelic acid. The sample is dissolved in a mixture of hydrofluoric, nitric, perchloric and sulfuric acids, the solution is evaporated to dryness, and the salts are dissolved in dilute hydrochloric acid. Zirconium mandelate is precipitated at 80°. The residual zirconium in the filtrate is recovered by heating at 80° overnight and the combined precipitates are ignited to Zirconium dioxide. An investigation was made of the factors involved in the dissolution of the sample, precipitation with mandelic acid, ignition of the precipitate, and size of sample. The effect of hafnium is discussed.     

The anilic acid number,an analytical index for testing dibasic acid anhydrides

For testing the purity of dibasic acid anhydrides and for analysing mixtures of these anhydrides with the corresponding free acids the determination of a new index number is recommended, indicated as the “anilic acid number”. The process is based on the fact that these acid anhydrides, when dissolved in acetone, under suitable experimental conditions can be added readily and quantitatively to aniline with resulting formation of the corresponding anilic acids.Immediately after addition, titration is effected with alcoholic potassium hydroxide on phenolphthalein. Pure dibasic acid anhydrides in this case yield the calculated anilic acid number. In the presence of free acids the values found are too high. The free acid content can be easily determined from the difference between the theoretical and the found anilic acid number.     

采用偏振塞曼原子吸收分析直接测定磷酸盐中微量铁

高浓度基体中测定微量铁时,排除基体干扰,多是采用络合萃取、沉淀分离等方法。Inovc等人用二巯基顺丁二氰与铁以1:3络合,其络合物与四丁基铵阳离子(tba⁺)生成离子对,用MIBK萃取后进行测定,手续繁杂费时,灵敏度仅为0.039μg/ml 1%abs,范键同志在测金属铬中的铁时,采用不分离的方法,溶样后直接测定,方法简单,但指出磷酸在火焰中对铁有抑制作用。     

Simultaneous microdetermination of carbon, hydrogen, chlorine, bromine, sulfur, and metals in organometallic compounds

A method for the simultaneous microdetermination of carbon, hydrogen, chlorine, bromine, sulfur, and metals which combines features of the known intermediate storage technique in organic microanalysis and formation of the metal-oxine complex, is described. Carbon and hydrogen are determined gravimetrically as usual. Sulfur and halogens are absorbed and stored on electrolytic silver. After completion of the combustion, the oxygen is replaced first by nitrogen and secondly by hydrogen which liberates the sulfur as sulfur dioxide and halogens as hydrogen halides and regenerates the silver layer. The liberated gases can be easily absorbed by dilute hydrogen peroxide and determined titrimetrically. The metal oxide, remaining in the platinum boat, is dissolved in a mixture of nitric-perchloric acids in a test tube and the metal content is determined gravimetrically and titrimetrically using 8-hydroxyquinoline.     

Study of the Reaction between Nucleic Acids and Tb-BPMPHD-CTMAB Complex and its Analytical Application

The direct use of the fluorescence emission properties of nucleic acids in the investigation of their biological properties is limited, whereas the use of metal complexes as fluorescence probe to study nucleic acids has increased remarkbly. Recently we found that the Tb-l,6-bi(1'-phenyl-3'-methyl-5'-pyrazolone-4'-)hezane-dione(BPMPHD)-trimethyl am-monium bromide(CTMAB) complex can be used as a sensitive fluorescence probe for the determination of nucleic acids.     

微波－气相－热压法分解高纯铂的研究

本文研究了微波气相热压法新技术分解高纯铂在密闭的聚四氟乙烯高压罐中，以微波瞬间加热混合酸产生的高压、纯净蒸气分解金属铂，此法避免了酸中杂质的沾污以制备供高纯铂分析的试液，提高了痕量杂质分析的准确度和降低检测限     

Determination of nickel,cobalt, copper and uranium in water by cathodic stripping chronopotentiometry with continuous flow

The potential of cathodic stripping chronopotentiometry for the determination of trace metals in a continuous-flow system is investigated. An automated analyzer with a fast rate of data acquisition (250 kHz) is described. The cathodic scans are preceded by adsorptive collection of surface-active metal complexes on the hanging mercury drop electrode. The scans are done by passing a constant current of between 0.8 (in deaerated solution) and 60 μA (in solutions saturated with air) through the working electrode. Copper, uranium, and nickel can be determined in the presence of dissolved oxygen, but the sensitivity for nickel is then much reduced. The sensitivity of stripping chronopotentiometry in the presence of dissolved oxygen is similar to that of fast linear-sweep voltammetry in the absence of dissolved oxygen. The limits of detection were 0.1 nM Ni, 0.1 nM Co, 1.8 nM Cu and 1.6 nM U, when the measurements were preceded by 60-s stirred adsorption; in the presence of dissolved oxygen the limit of detection for nickel was higher at 0.6 nM, and cobalt could not be determined, as its peak was located on top of the oxygen peak. The determinations of copper and uranium were not adversely affected by dissolved oxygen. The limits of detection can be lowered further by using a prolonged collection period (up to 300 s). The technique was successfully tested by measuring nickel with continuous flow in water pumped on board of a small vessel in the Tamar estuary.     

聚二烯丙基二甲基氯化铵与核酸相互作用的共振光散射光谱及分析应用

实验基于核酸与聚阳离子聚二烯丙基二甲基氯化铵(PDDA)的相互作用导致共振光散射(RLS)增强的现象来测定核酸。考察了pH值、PDDA浓度和离子强度对体系共振光散射强度的影响。在优化条件下,建立了用RLS光谱测定微量核酸的新方法。方法的抗干扰能力较强,可允许大部分的常见金属离子、核苷酸、氨基酸、糖、蛋白质等干扰物质的存在。同时用于合成样品的分析,结果令人满意。     

Determination of boron in nickel-base alloys by the dianthrimide method

The dianthrimide method for the determination of boron in iron and low-alloy steels may be applied to nickel-base materials. The sample is dissolved, without any loss of boron, by hydrochloric and sulphuric acids and the resulting boric acid determined spectrophotometrically with dianthrimide. Background corrections are necessary to compensate for the absorbance from ions such as nickel and iron.     

Functional speciation of metal-dissolved organic matter complexes by size exclusion chromatography coupled to inductively coupled plasma mass spectrometry and deconvolution analysis

High performance size exclusion chromatography coupled to inductively coupled plasma mass spectrometry (HP-SEC–ICP-MS), in combination with deconvolution analysis, has been used to obtain multielemental qualitative and quantitative information about the distributions of metal complexes with different forms of natural dissolved organic matter (DOM). High performance size exclusion chromatography coupled to inductively coupled plasma mass spectrometry chromatograms only provide continuous distributions of metals with respect to molecular masses, due to the high heterogeneity of dissolved organic matter, which consists of humic substances as well as biomolecules and other organic compounds. A functional speciation approach, based on the determination of the metals associated to different groups of homologous compounds, has been followed. Dissolved organic matter groups of homologous compounds are isolated from the aqueous samples under study and their high performance size exclusion chromatography coupled to inductively coupled plasma mass spectrometry elution profiles fitted to model Gaussian peaks, characterized by their respective retention times and peak widths. High performance size exclusion chromatography coupled to inductively coupled plasma mass spectrometry chromatograms of the samples are deconvoluted with respect to these model Gaussian peaks. This methodology has been applied to the characterization of metal–dissolved organic matter complexes in compost leachates. The most significant groups of homologous compounds involved in the complexation of metals in the compost leachates studied have been hydrophobic acids (humic and fulvic acids) and low molecular mass hydrophilic compounds. The environmental significance of these compounds is related to the higher biodegradability of the low molecular mass hydrophilic compounds and the lower mobility of humic acids. In general, the hydrophilic compounds accounted for the complexation of around 50% of the leached metals, with variable contributions of humic and fulvic acids, depending on the nature of the samples and the metals.     

Electrochemical stripping determination of traces of copper, lead, cadmium and zinc in zirconium metal and zirconium dioxide

Procedures have been developed for the determination of copper, lead, cadmium and zinc in zirconium metal and zirconium dioxide, at concentrations of 1 ppm or less. Zirconium metal was dissolved in suphuric acid, and zirconium dioxide decomposed under pressure with hydrofluoric acid. Sample solutions were prepared in dilute sulphuric acid. For the stripping determination, the sample solution was either mixed with a complexing tartrate base electrolyte or the pre-electrolysis was carried out in acid solution, with the acid solution being exchanged for a pure base electrolyte (e.g. an acetate buffer) for the stripping step. The stripping step was monitored by d.c., differential pulse and Kalousek commutator voltammetry and the three methods were compared. A stationary mercury-drop electrode can generally be used for all the methods, whereas a mercury-film electrode is suitable only for the d.c. voltammetric determination of copper, lead and cadmium, as pulse measurements with films are poorly reproducible and the electrodes are easily damaged. The relative standard deviation does not exceed 20%. Some samples contained relatively large amounts of copper, which is best separated by electrodeposition on a platinum electrode.     

Atomic absorption spectrometric determination of trace zinc in alloys and biological samples after preconcentration with [1-(2-pyridylazo)-2-naphthol] on microcrystalline naphthalene

An atomic absorption spectrometric method for the determination of trace amounts of zinc after adsorption of its [1-(2-pyridylazo)-2-naphthol] complex on microcrystalline naphthalene has been developed. This complex is adsorbed on microcrystalline naphthalene in the pH range 3.5-7.5 from large volumes of aqueous solutions of various alloys and biological samples with a preconcentration factor of 40. After filtration, the solid mass consisting of the zinc complex and naphthalene was dissolved with 5 ml of dimethylformamide and the metal was determined by flame atomic absorption spectrometry. Zinc can alternatively be quantitatively adsorbed on [1-(2-pyridylazo)-2-naphthol]-naphthalene adsorbent packed in a column and determined similarly. About 0.5 ng of zinc can be concentrated in a column from 200 ml of aqueous sample, where its concentration is as low as 2.5 pg ml-1. The calibration curve is linear in the range 0.1-6.5 ng ml-1 in dimethylformamide solution. Eight replicate determinations of 2 ng ml-1 of zinc gave a mean absorbance of 0.145 with a relative standard deviation of 1.5%. The sensitivity for 1% absorption was 0.061 ng ml-1. Various parameters, such as the effect of pH and the interference of a number of metal ions on the determination of zinc, have been studied in detail to optimize the conditions for the determination of zinc in various standard complex materials.     

Non-aqueous redox titrations with iodine and iodine halides. Determination of xanthates and dithiocarbamates

Summary Iodine and iodine halides (monobromide, monochloride and trichloride) solutions in acetonitrile have been used as oxidimetric reagents for the visual and potentiometric determination of alkali metal salts of xanthic and dithiocarbamic acids also dissolved in acetonitrile. The methods are simple, accurate, rapid and widely applicable.

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Zusammenfassung Jod und dessen Halogenverbindungen (Monobromid, Monochlorid und Trichlorid) in Acetonitril gelöst wurden als oxydimetrische Reagenzien zur visuellen und potentiometrischen Titration von Alkali-Xanthogenaten und-dithiocarbamidaten in dem genannten Lösungsmittel verwendet. Das Verfahren ist einfach, genau und vielseitig anwendbar.