Rapid coprecipitation-separation and flame atomic absorption spectrometric determination of lead and cadmium in water with cobalt (II) and ammonium pyrrolidine dithiocarbamate

A coprecipitation technique which does not require complete collection of the precipitate was proposed for the determination of trace lead and cadmium in water with flame atomic absorption spectrometry (FAAS) after preconcentration of lead and cadmium by using cobalt (II) and ammonium pyrrolidine dithiocarbamate (Co-APDC) as coprecipitant and known amount of cobalt as an internal standard. Since lead, cadmium and cobalt were well distributed in the homogeneous precipitate, the concentration ratio of lead to cobalt, and cadmium to cobalt remained unchanged in any part of the precipitate. The amount of lead and cadmium in the original sample solution can be calculated respectively from the ratio of the absorbance values of lead and cadmium to cobalt in the final sample solution that is measured by FAAS and the known amount of the lead and cadmium in the standard series solutions. The optimum pH range for quantitative coprecipitation of lead and cadmium is from 3.0 to 4.5. The 16 diverse ions tested gave no significant interferences in the lead and cadmium determination. Under optimised conditions, lead ranging from 0 to 40?µg and cadmium ranging from 0 to 8?µg were quantitatively coprecipitated with Co-APDC from 100?mL sample solution (pH?～?3.5). This coprecipitation technique coupled with FAAS was applied to the determination of lead and cadmium in water samples with satisfactory results (recoveries in the range of 94.0–108%, relative standard deviations <6.0%).     

Determination of cobalt and nickel by graphite-furnace atomic absorption spectrometry after coprecipitation with scandium hydroxide.

Trace amounts of cobalt and nickel in a water sample were quantitatively coprecipitated with scandium hydroxide at pH 8.0-10.5. Because the coprecipitant could be easily dissolved with 1 mol dm(-3) nitric acid, and the presence of up to 10 mg cm(-1) of scandium did not interfere with the graphite-furnace atomic absorption spectrometric determination of cobalt and nickel, the volume of the final solution prepared for the determination could be minimized down to 0.5 cm3. The concentration factor was 400-fold and the detection limits (signal to noise = 2) were 5.0 pg cm(-3) of cobalt and 10.0 pg cm(-3) of nickel in 200 cm3 of the initial sample solution. The 27 diverse ions investigated did not interfere with the determination in at least a 500-fold mass ratio to cobalt or nickel. The proposed method was successfully applied to the determination of trace amounts of cobalt and nickel in river-water samples.     

Synthesis and characterization of large colloidal cobalt particles

Large colloidal environmentally stable silica-coated cobalt particles were synthesized by combining the sodium borohydride reduction in aqueous solution and the St?ber method. Low size polydisperse cobalt spheres with an average size of 95 nm were synthesized by using a borohydride reduction method and were subsequently coated with a thin layer of silica by means of hydrolysis and condensation of tetraethylorothosilicate (TEOS) in an aqueous/ethanolic solution. The large uniform cobalt spheres consist of smaller metallic Co clusters, explaining the superparamagnetic behavior of the spheres. The particles were investigated by transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM).     

电感耦合等离子体质谱法同时测定地质样品中镉、锗、钴

建立电感耦合等离子体质谱法同时测定地质样品中镉、锗、钴含量的分析方法。样品用氢氟酸-硝酸混合溶液加热溶解,然后加热浓缩驱酸,再用硝酸溶液(1+1)复溶提取,在选定的仪器工作条件下进行测定。镉、锗、钴的含量分别在0.00~0.10,0.00~5.00,0.00~50.00 μg/g范围内与质谱峰强度呈良好的线性关系,相关系数均大于0.999,方法检出限分别为0.01,0.02,0.02 μg/g。用该方法对国家一级标准物质进行测定,测定值的相对误差均小于10%,测定结果的相对标准偏差为0.79%~8.45%(n=12)。该方法样品处理过程简便,检测效率高,适用于批量地质样品中镉、锗、钴的测定。     

Determination of nickel and cobalt in natural waters and biological material by reductive chronopotentiometric stripping analysis in a flow system without sample deoxygenation

The instrumental set-up consists of a thin-layer cell with a glassy carbon working electrode and an inlet valve by means of which six different solutions can be sucked through the cell. The system is controlled by a microprocessor and suction is provided by means of a peristaltic pump. In the first step of the analytical cycle, a mercury film is plated onto the glassy carbon electrode and then the sample solution is allowed into the cell and nickel(II) and cobalt(II) are potentiostatically adsorbed onto the mercury film as their dimethylglyoxime complexes. Nickel(II) and cobalt(II) are then reduced in a medium of 5 M calcium chloride by means of constant current and simultaneously the microprocessor records the potential vs. time behaviour of the working electrode. Finally the mercury film is removed by mild oxidation in an iodine/iodide solution and the glassy carbon surface is cleaned with ethanol and sodium hydroxide prior to the next analytical cycle. The cobalt(II) and nickel(II) concentrations are evaluated by means of a standard addition procedure. The technique was applied to drinking, estuarine and sea water samples. The detection limits on the one sigma level after one minute of potentiostatic adsorption were 9 and 11 ng l^?1 for nickel(II) and cobalt(II), respectively. Nickel(II) and cobalt(II) were determined in reference samples of bovine liver and sea-water sediments after acid digestion. In order to obtain correct cobalt values, it was necessary to reduce cobalt(III) species formed during the acid digestion with sodium tetrahydroborate.     

Determination of cobalt and zinc in highpurity niobium, tantalum, molybdenum and tungsten metals by atomicabsorption spectrophotometry after separation by extraction

A method for determining 0.0005-0.05% of cobalt and zinc in high-purity niobium, tantalum, molybdenum and tungsten metals by atomic-absorption spectrophotometry is described. After sample dissolution, cobalt and zinc are separated simultaneously from the matrix materials by chloroform extraction of their thiocyanatediantipyrylmethane ion-association complexes, at pH 3.25, from a citric acid medium approximately 1.2M in sodium thiocyanate. Interference from copper is eliminated with thiourea. Large amounts of iron interfere under the recommended conditions, but moderate amounts may be present in the sample solution without causing appreciable error in the results. Phosphorus (as orthophosphate) interferes in the extraction of cobalt from tungsten solutions. Moderate amounts of other impurities do not interfere in the proposed method.     

Simultaneous Preconcentration of Copper,Nickel and Cobalt In Water By Coprecipitation-Flotation For Electrothermal Atomic Absorption Spectrometry

Abstract

A method is described for the simultaneous flotation separation and determination of μg-levels of copper (II), nickel (II) and cobalt (II) in water. Copper, nickel and cobalt in a 1000-ml sample of water are coprecipitated with hydrated zirconium oxide at pH 9.1±0.1. The precipitate is floated with the aid of a surfactant solution and small air bubbles, separated and dissolved in dilute hydrochloric acid. The contents of these elements are determined by electrothermal atomic absorption spectrophotometry. The method is applied to the determination of low μg/1 levels of copper, nickel and cobalt in fresh water.     

Determination of ultra-trace levels of cobalt by ion chromatographic separation and chemiluminescence detection

A luminol chemiluminescence detection/flow injection analysis technique coupled with ion chromatography (IC) has been examined for the selective determination of cobalt (II) at pg ml^?1 levels. A barium chloride solution was used as an eluent in the IC to separate cobalt(II) from interferents. When a 100-μ1 sample injection volume was used, the detection limit was 1.0 pg ml^?1 cobalt; the minimum detectable amount of cobalt was 100 fg. The calibration graph was linear above 10 pg ml^?1 and the linear dynamic range extended over six orders of magnitude. The relative standard deviation for ten replicate measurements of 30 pg ml^?1 cobalt was 3.8%. The results of the analysis of a synthetic sample corresponding to a boiling-water reactor coolant and some commercially available copper(II) standard solutions are given.     

Determination of radioactive and stable cobalt in marine biological materials (author's transl)]

Studies were made to develop the method for rapid determination of radioactive and stable cobalt in a single specimen of marine biological materials. The sample was dried, ashed, and dissolved in acid. The cobalt was extracted with 1-nitroso-2-naphthol benzene and determined by absorptiometry on the benzene phase. Then, the organic solution was evaporated to dryness, and the residue was treated with nitric-perchloric acid mixture to decompose any organic matter, and taken up with hydrochloric acid. The cobolt was extracted from the solution with TIO A-toluene, and the radioactive cobalt was determined by liquid scintillation counting on the toluene phase. Examinations were made on the chemical yield and on the decontamination factor of the fission product nuclides. Analysis were made on the marine biological samples of Urazoko Bay, Fukui prefecture. Agreement of the radioactive cobalt data between that by the present method and that by Ge(Li) gamma ray spectometry was good. Also, the stable cobalt value by the present method agreed well with that by neutron activation analysis method.     

Dispersive liquid–liquid microextraction and spectrophotometric determination of cobalt in water samples

A new simple and rapid dispersive liquid–liquid microextraction has been applied to preconcentrate trace levels of cobalt as a prior step to its determination by spectrophotometric detection. In this method a small amount of chloroform as the extraction solvent was dissolved in pure ethanol as the disperser solvent, then the binary solution was rapidly injected by a syringe into the water sample containing cobalt ions complexed by 1-(2-pyridylazo)-2-naphthol (PAN). This forms a cloudy solution. The cloudy state was the result of chloroform fine droplets formation, which has been dispersed in bulk aqueous sample. Therefore, Co-PAN complex was extracted into the fine chloroform droplets. After centrifugation (2 min at 5000 rpm) these droplets were sedimented at the bottom of conical test tube (about 100 µL) and then the whole of complex enriched extracted phase was determined by a spectrophotometer at 577 nm. Complex formation and extraction are usually affected by some parameters, such as the types and volumes of extraction solvent and disperser solvent, salt effect, pH and the concentration of chelating agent, which have been optimised for the presented method. Under optimum conditions, the enhancement factor (as the ratio of slope of preconcentrated sample to that obtained without preconcentration) of 125 was obtained from 50 mL of water sample, and the limit of detection (LOD) of the method was 0.5 µg L^?1and the relative standard deviation (RSD, n = 5) for 50 µg L^?1 of cobalt was 2.5%. The method was applied to the determination of cobalt in tap and river water samples.     

Simultaneous determination of radioactive and stable isotopes of cobalt in environmental samples by the isotopic exchange method

The isotopic exchange method is studied for the simultaneous determination of radioactive and stable isotopes of cobalt in environmental samples. Radioactive cobalt is isotopically exchanged with Co-CyDTA in HC1 solution of the sample. The solvent extraction method is used for the separation of Co2+ and Co-CyDTA species from each other. The amounts of radioactive and stable cobalt isotopes are calculated with activities of Co and Co-CyDTA at the exchange equilibrium. The methods for eliminating interfering ions are discussed. The results are in good concordance with those obtained by the conventional analytical methods.     

Determination of radioactive cobalt in reactor coolant water by solvent extraction

A rapid extraction separation method is described for the radiochenaical determination of cobalt-58 and cobalt-60 in reactor coolant water. After adjustment of the pH of the sample water to 5.0-5.5, cobalt diethyldithiocarbamate is extracted with benzene. Other nuclides, e.g., manganese-54 and -56, copper-64 and iron-59, which are usually present in reactor coolant water, are also extracted together with cobalt. However, they can be readily removed by washing the extract with mercury(II) chloride solution. The cobalt-58 and -60 activities are measured by gamma counting of an aliquot of the washed extract. Trace amounts of radioactive cobalt in 500 ml of sample water can be quantitatively extracted without the use of carrier. The separation could be finished in 15 min and an average recovery of 99.5 % was obtained, with a relative standard deviation of 1.4% (25 experiments).     

Silaned glass beads for the preconcentration and spectrophotometric determination of cobalt with 2-(2-pyridylazo)-5-diethylaminophenol

Silaned glass beads are applied for the preconcentration and spectrophotometric determination of cobalt with 2-(2-pyridylazo)-5-diethylaminophenol (PADAP). Traces of cobalt are collected as the coloured PADAP complex on a column of the beads, and the complex is then eluted with a small volume of ethanol-hydrochloric acid mixture and the absorbance of the eluate is measured at 575 nm. The cobalt can easily be concentrated by a factor of 50-500 in this way, and 0.1-2 mug of cobalt in 100 ml of sample solution can be determined reproducibly. High concentrations of Fe(III), Cr(III), Pb, Zn, Cu(II), Mn(II), Cd, Al, Ca and Mg can be tolerated but Pd(II) interferes.     

Spectrophotometric determination of iron and cobalt with Ferrozine and dithizone

Procedures are described whereby iron (1–50 μg) and cobalt (1–25 μg) are determined spectrophotometrically, iron as iron(II) with the disodium salt of 3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine (Ferrozine) and cobalt as the cobalt(III) dithizonate complex. The reduction to iron(II) prevents interference of iron(III) in the cobalt determination, and both metals can be determined in the same portion of sample solution. Removal of interference by other metal ions is described.     

Preconcentration of cobalt using Amberlyst 36 as a solid-phase extractor and its determination in various environmental samples by flame atomic absorption spectrometry

A new and simple column-solid-phase extraction method has been developed to separate and preconcentrate trace cobalt in water and soil prior to its determination by flame atomic absorption spectrometry (FAAS). Different factors such as pH of sample solution, sample volume, amount of resin, flow rate of aqueous solution, volume and concentration of eluent, and matrix effects for preconcentration were optimized. Under optimized experimentally established conditions, an analytical detection limit of 0.44?µg?L^?1, precision (RSD) of 1.9%, enrichment factor of 200, and capacity of resin of 82?mg?g^?1 were obtained. The method was applied for cobalt determination by FAAS in tap water, natural drinking water, soil, and roadside dust samples. The accuracy of the method is confirmed by analysing standard reference material (Montana Soil, SRM 2711).     

8-喹啉偶氮显色剂QADCB的合成及其分析性能的研究

报道了8-喹啉偶氮显色剂2-(8-喹啉偶氮)-5-二羧甲氨基苯甲酸(QADCB)的合成、提纯与鉴定,研究了其与Co(Ⅱ)、Ni(Ⅱ)、Fe(Ⅲ)的显色反应,对QADCB与Co(Ⅱ)的显色反应作了研究。在pH5.9的缓冲体系中,试剂与Co(Ⅱ)形成棕红色配合物,其最大吸收波长位于650nm,表观摩尔吸光系数为4.2×104L.mol-1.cm-1,钴量在0~20μg/25mL范围内符合比耳定律。方法简便、快速,选择性较好,已用于纯铜、维生素B12中微量钴的测定,结果满意。     

Determination of cobalt in zinc electrolyte by an automated flow-injection system

A flow-injection method has been developed for the spectrophotometric determination of cobalt in zinc electrolyte using 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)aniline (5-Br-PSAA) as chromogenic reagent. A sample solution is injected into a carrier containing hydrochloric acid, diammonium hydrogenphosphate and hydrogen peroxide. The sample is then merged with the stream of ammonium acetate solution and PSAA solution is synclonously injected into the sample zone. After mixing with 2M sulphuric acid, the absorbance of cobalt-PSAA complex is measured at 617 nm. The flow injection system proposed is fully controlled with a personal computer. The flow-injection system permits throughput of 12 samples per hour. The relative standard deviation (n = 10) for 0.1 mug Co/ml solution is 5.0%.     

Determination of trace amounts of cobalt(II) by flow injection-solid phase spectrometry (FI-SPS) with 5-Br-PADAB.

Flow injection-solid phase spectrometry (FI-SPS) has been applied to the determination of cobalt(II) in water samples. The complex formed between cobalt and 5-Br-PADAB was on-line protonated and concentrated on an AG 50W-X2 cation-exchanger in a flow-through cell. The increase in absorbance caused by the accumulation of the complex in the resin was continuously measured. The interference by copper could be effectively eliminated by using EDDP as a masking agent. The detection limit was 40 ng dm(-3) with a 4.0 cm3 sample solution.     

Solid-phase extraction and atomic absorption spectrometric determination of cobalt using an octadecyl bonded silica membrane disk modified with Cyanex 272

A simple SPE method for determination of cobalt(II) using a C18 bonded silica membrane disk impregnated with Cyanex 272 has been developed. Cobalt(II) was quantitatively sorbed at pH 6.0 from a sample solution and eluted using 10.0 mL 1.0 M HNO3 prior to its flame atomic absorption spectrometric determination. The influence of eluting agents, the minimum volume and maximum flow rate of the eluent, and interfering ions on cobalt(II) was studied. The method developed for cobalt(II) had an LOD of 1.4 microg/L, and a preconcentration factor > 200 with an RSD of 0.6%. The reusability of the modified disk was for 40 cycles. The method was applied for the determination of cobalt in certified samples, urine, and industrial sludge samples.     

High enrichment method for the determination of ultra-trace levels of cobalt by liquid—liquid extraction using water/oil/water emulsions as liquid surfactant membranes

A high preconcentration method for the determination of cobalt by graphie furnace atomic absorption spectrometry using liquid surfactant membranes was developed. Droplets of dilute hydrochloric acid in kerosene containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester emulsion coated with sorbitan monooleate are dispersed in an aqueous sample solution. Cobalt(II) diffuses through the liquid membrane to form the complex with the ester and the analyte ion is extracted successively into the inner acidic aqueous phase. A 550-fold enrichment of cobalt(II) and a detection limit of 10 pg ml^?1 are achieved.