Determination of submicrogram quantities of ruthenium by catalysis of the cerium(iv)-arsenic(iii) reaction

Ruthenium in amounts of 0 005–0 1 μg (and less if need be) can be determined by its catalysis of the slow reaction between cerium(IV) and arsenic(III) in sulfuric acid solution The rate of the catalyzed reaction is obtained by measuring the concentration of cerium(lV) spectrophotometrically as a function of the time Ruthenium is first separated by carbon tetrachloride extraction of the tetroxide, following argentic oxide oxidation Osmium tetroxide is removed by prior extraction with carbon tetrachloride after differential oxidation with nitric acid Osmium can also be removed by boiling an acid solution with hydrogen peroxide, ruthenium being left in solution     

Direct determination of submicrogram amounts of osmium and ruthenium in sulphide ores by neutron activation analysis

A neutron activation method, involving a radiochemical separation based upon two consecutive distillations, is described for the direct determination of nanogram amounts of osmium and ruthenium in selected sulphide ores. A loss of osmium due to volatilization occurred when the tracer solution was evaporated. A simple radiochemical method using iron(III) hydroxide precipitation was devised to prevent this loss. The proposed method was applied to ores expected to contain only traces of platinum metals. The addition of the active carrier was found to improve the separation of these two metals in the submicrogram range, although, no chemical yield determination was necessary.     

Cyclic voltammetry of nucleic acids and determination of submicrogram quantities of deoxyribonucleic acids by adsorptive stripping voltammetry

In cyclic voltammetry (at a mercury drop electrode) guanine residues in the polynucleotide chain give a characteristic anodic peak at potentials close to ?0.3 V (vs. saturated calomel electrode). At low concentrations of polynucleotide, this peak can be enhanced substantially if the potential scan is preceded by adsorptive preconcentration of the polynucleotide at the hanging mercury drop electrode. With accumulation times shorter than 10 min at pH 6.8, the limit of detection of a single-stranded polynucleotide is < 0.1 μg ml^?1. The peak of double-helical deoxyribonucleic acid (DNA) is considerably lower than that of single-stranded DNA under the same conditions, which can be exploited to determine low concentrations of single-stranded DNA in the presence of double-stranded DNA.     

Spectrophotometric procedure using rhodamine B for determination of submicrogram quantities of antimony in rocks

A spectrophotometric procedure using Rhodamine B is given for the determination of antimony in mineralized rocks after its separation as stibine. A study of the Rhodamine B reaction points to the importance of the order of addition of reagents in enhancing sensitivity and increasing the stability of the system. The tolerance of some 26 elements is established for the overall procedure. Although the limit of determination is approximately 0.5 ppm Sb in a 0.2-g sample, the procedure is intended primarily for screening samples containing more than 1 ppm Sb. In pure solutions 0.1 mug of antimony can be determined with a relative standard deviation of 25%. For >0.2 mug of antimony a relative standard deviation of 15% or less can be expected.     

Detection of submicrogram quantities of glycosaminoglycans on agarose gels by sequential staining with toluidine blue and Stains-All

A sensitive method has been developed for the visualization of nonradiolabelled glycosaminoglycans resolved by agarose gel electrophoresis using staining with toluidine blue followed by Stains-All procedure. This method, which can detect as little as 10 ng of a single species, can be used to stain a few micrograms of a complex polysaccharide mixture. The combination of agarose gel electrophoresis and sequential toluidine blue/Stains-All staining can be applied to the analysis of all the complex glycosaminoglycans (i.e., heparin, heparan sulfate, chondroitin/dermatan sulfate) and nonsulfated polyanions (i.e., hyaluronate, defructosylated capsular polysaccharide K4) as well as to comparisons of specificities of the glycosaminoglycan-degrading enzymes and the identification and quantification of the contaminations of other polysaccharides within glycosaminoglycan preparations with great sensitivity (about 0.1%). Furthermore, this method can be used to stain low-molecular-mass fractions and oligosaccharides derived from the natural polyanions, such as heparin. This procedure may be particularly valuable in situations where the availability of glycosaminoglycan is very limited.     

Determination of osmium by the sorption-X-ray fluorescence technique

Sorption of osmium(IV, VI) on complexing sorbents POLYORGS XXIV, POLYORGS 32 M, and POLYORGS 32 V and on the PVA-PGMA-PEPA sorbent from alkaline and hydrochloric acid solutions is studied. It is demonstrated that equilibrium in systems under study is attained within 40 min for the POLYORGS XXIV sorbent and within 2.5 h for the POLYORGS 32 V sorbent and that the sorbents exhibit a sufficiently high sorptive capacity with respect to osmium: from 3.4 to 8 mg of Os(VI) in alkaline solutions and 2.2 mg of Os(IV) in acidic solutions. Optimal conditions of analysis of a concentrate on an EDX-771 energy-dispersive X-ray fluorescence spectrometer are revealed and, on this basis, a sorption-X-ray fluorescence method that provides the determination of osmium in a wide concentration range with the detection limit down to 10^-6% is developed.     

Sensitive spectrophotometric kinetic determination of osmium by catalysis of the pyrogallol red-bromate reaction

Osmium(VIII) is determined by means of its catalytic effect on the oxidation of pyrogallol red (PGR) by potassium bromate at pH 6.0, 30°C and 545 nm. The decrease in absorbance of PGR (2.5 × 10^?5 M) in the presence of KBrO₃ (0.20 M) over a period of 0–150 s is proportional to the concentration of osmium(VIII) over the range 0–1400 ng ml^?1. The limit of detection of osmium was 0.65 ng ml^?1. The precision and accuracy of the method are described. The effects of the presence of 45 cations and anions on osmium determination were studied. The effects of probable interferences were completely removed by a single extraction of osmium as osmium tetraoxide into isobutyl methyl ketone and back-extraction into sodium hydroxide solution.     

Determination of submicrogram amounts of gallium by ion-exchanger fluorimetry Determination of gallium in natural waters

A method for microdetermination of gallium at ng/ml level has been developed, based on ion-exchanger fluorimetry. The gallium reacts with salicylidene-o-aminophenol to give a highly fluorescent complex, which is fixed on a dextran-type cationic resin. The fluorescence of the resin, packed in a 1-mm silica cell, is measured directly with a solid-surface attachment. The range of concentration of the method is 2.0-10.0 ng/ml, the RSD 1.3% and the detection limit 0.3 ng/ml. The method has been applied to the determination of gallium in natural waters. The gallium content found in tap water was higher than that in raw water. This is related to the use of commercial aluminium salts in the water-treatment plant.     

Determination of submicrogram amounts of tin by atomic absorption spectrometry with electrothermal atomization

The determination of tin is described with particular reference to the addition of organic compounds to the graphite tube for the suppression of interferences of other ions. Most were suppressed by adding 20 μl of 10% ascorbic acid to 20 μl of sample in the furnace. The method was used for the determination of tin in waste-waters and sediments.     

Determination of microgram quantities of gadolinium by cathode-ray polarography

A cathode-ray polarographic method has been developed for the determination of microgram quantities of gadolinium with the use of an azo-dye, Solochrome Violet RS. Disadvantages in the use of 0sd1M potassium chloride, commonly recommended as electrolyte for the polarographic determination of rare earths, have been demonstrated. The influence of pH, temperature, ligand concentration and purity, and the stability of the complex, have been investigated for the optimum performance of the method. The linear range is 0.5-12 mug/ml of gadolinium. Interferences by some lanthanides and other cations have been examined.     

Determination of nanogram quantities of uranium by pulsed-laser fluorometry

Summary A versatile, direct method for the determination of trace amounts of uranium in solution has been developed utilizing pulsed-laser fluorometry and a pyrophosphate fluorescence enhancing reagent. Measurements with a 2–3% relative standard deviation and accurate to better than 1% have been obtained in the 0.01 to 4g U/g range. The detection limit is 0.005 ng uranium. Time required per determination is 6 min. A special feature of the method is the use of a standard addition technique to eliminate sample matrix effects. The effects of temperature, acidity, reagent impurity and anionic impurities have been studied.

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Bestimmung von Nanogramm-Mengen Uran mit Hilfe eines Laser-Fluorometers

Zusammenfassung Eine Direktmethode zur Bestimmung von Uranspuren in Lösungen mit Hilfe der Laser-Fluorometrie und eines fluoreszenz-anregenden Pyrophosphates wurde entwickelt. Die Messungen erfolgen mit einer rel. Standardabweichung von 2–3% und einer Genauigkeit besser als 1% bei Mengen von 0,01–4g U/g. Die Nachweisgrenze beträgt 0,005 ng U. Eine Bestimmung dauert 6 min. Um Matrix-Effekte zu vermeiden, verwendet man die Standard-Zusatz-Technik. Der Einfluß der Temperatur, der Acidität und etwaiger Verunreinigungen wurde untersucht.

     

发射光谱法测定锇中贵金属杂质

锇在地球上含量比稀有金属还要低。文献曾报道了用化学光谱法进行测定[1 ] ,但此方法繁琐 ,耗时颇长。锇是一种高熔点元素 ,同其它铂族金属一样可以制成海绵状金属 ,可采用粉末试样光谱分析法进行分析。不同之处是 ,锇在空气中常温下就能被氧化成有毒氧化物四氧化锇 ;在加热到 80 0℃时 ,便迅速氧化成剧毒气体 ,达到一定浓度便会刺激眼睛 ,引起视力模糊 ,甚至失明。因此 ,采用一种通风良好、样品和标样密封保存、摄谱时加置安全防护罩的发射光谱法测定锇中杂质元素的分析方法。操作简便 ,优于常用方法检出限的分析方法。1　实验部分1 1　仪…     

Determination of trace quantities of selenium by indirect atomic-absorption spectrophotometry

The selenium(IV)-iodide interaction in acid medium, leading to the liberation of iodine, has been utilized for the indirect determination of selenium by atomic-absorption spectrophotometry (AAS). The iodine is extracted into benzene and subsequently reductively stripped into an aqueous solution of ascorbic acid. After extraction of the resulting iodide as tris(1,10-phenanthroline)cadmium(II) iodide into nitrobenzene, the cadmium content of the organic extract is determined by AAS. Beer's law is applicable up to 0.75 ppm of selenium. The few interferences are readily overcome. The chemical yield in the system is about 80% overall.     

Determination of trace quantities of tin by neutron activation analysis

A neutron activation method of general applicability has been developed for determining traces of tin in a variety of samples. The samples and comparative standards, sealed into ampoules, are irradiated intermittently for 3 days at a neutron flux of ca, 3 · 10¹¹ n/cm²/sec, followed by carrier radiochemical separations mainly consisting of solvent extraction steps. As little as 0.1 μg Sn can be easily determined by comparing the induced β-activity of ¹²¹Sn (27.5 h) with that of a standard, The method is rapid and has a reasonably high chemical yield of about 50%. Results are quoted for the tin contents of a number of materials including silicate rocks, sea waters, biological materials and steels.     

Determination of ultratrace quantities of uranium by laser-induced fluorescence spectrometry

Uranium (1.5–12 ng l^?1) is co-precipitated with calcium fluoride, the precipitate is ignited in air, and the uranium fluorescence induced by a pulsed nitrogen laser is measured. The detection limit is 0.5 ng l^?1 uranium. Iron(III) and lead interfere seriously.     

Determination of osmium in waste water by graphite furnance atomic absorption spectrometry

The determination of osmium in waste water by electrothermal atomic absorption spectrometry (AAS) with a graphite furnace atomiser has been investigated. The atomisation characteristics of osmium on the atomiser were found to result in optimal ashing and atomisation temperatures of 300–500 and 3180 °C, respectively.The characteristic mass (the mass of element giving 0.0044 abs.) of osmium after optimization was found to be 1.6ng, which is better than obtained with flame AAS and ultraviolet/visible (UV) absorption spectrophotometry. The detection limit (s/n = 3) was 3.6ng (or 0.36 (g ml^–1). The relative std. deviation obtained with graphite furnace AAS was 3.0%.The interference caused by large amounts of common cations and anions in waste water were evaluated and thiourea as matrix modifier was shown to be able to eliminate many interferences. The recovery of osmium spiked in waste water was considered almost satisfactory at the 1–50 g ml^–1 range and the results were shown to well agree with the analytical values obtained by UV absorption spectrophotometry.     

Determination of small quantities of xanthate

A new spectrophotometric method for the determination of very small amounts of xanthate in solutions, particularly cyanide solutions from gold-extraction plants, is described. It is based on the formation and extraction of copper(II) xanthate. The coefficient of variation is 1.0% at the 40-ppm level and 3.4% at the 4-ppm level and the lower limit of determination is approximately 0.5 ppm. Copper(II) xanthate normally decomposes into copper(I) xanthate and dixanthogen, but in the proposed method the decomposition is delayed.