High performance ultra trace analysis in molybdenum and tungsten accomplished by on-line coupling of ion chromatography with simultaneous ICP-AES

For the characterisation of trace elements in high purity Mo and W analytical methods with a detection limit in the ng/g-range have to be used. Today mass spectrometric methods are state of the art for such applications. However, these methods in case of refractory metal analysis are time consuming, expensive, limited by isobaric interferences and therefore not very suitable for quality control in an industrial laboratory. With respect to these drawbacks a cost and time efficient method was developed by on-line coupling of an ion chromatographie system to a simultaneous ICP-AES (Inductively Coupled Plasma — Atomic Emission Spectrometry) instrument. Within the limitations caused by the hard- and software of the system all parameters such as eluent concentration and flow rate, nebulizer and plasma gas flow, sampling frequency, integration time and the number of simultaneously measured emission lines were optimised. Further enhancement of the sensitivity was achieved by the use of an ultrasonic nebulizer pushing the detection limits down to the pg/g- and ng/g-range for 22 representative elements.Dedicated to Professor Dr. rer. nat. Dr. h. c. Hubertus Nickel on the occasion of his 65th birthday     

On-line coupling of atomic spectrometry and ion chromatography with time resolved registration as a new tool for ultra trace analysis in refractory metals

Summary On-line coupling of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Ion Chromatography (IC) offers unique features for ultra trace analysis. With an on-line preconcentration procedure based on cation exchange, sub-ng/g analysis is possible in complex matrices like molybdenum and tungsten. Results match with isotope dilution mass spectrometry (IDMS) and are comparable with glow discharge mass spectrometry (GDMS). The optimal dissolution reagent for these matrices is hydrogen peroxide whose clean up to ultra high purity is possible with metal-free chromatographic equipment. All elements with cationic chemistry can be preconcentrated in acidic peroxide solutions. In this study 21 elements are measured which are detrimental for microelectronic applications. The absolute detection limits of the IC-ICP combination, with time resolved registration, are at the lower ng-level. The reproducibility is not significantly lowered by the coupling, but a ten-fold sensitivity enhancement is observed in comparison to chemically similar off-line trace-matrix-separations. Other features are simultaneous matrix corrections, use of monitors lines for method enhancement, error recognition and correction using time resolved measurement and simple calibration of the method with aqueous standards.     

On-line coupling of ion chromatography and atomic spectrometry for ultra trace analysis in high purity molybdenum- and tungsten-silicide

The well-established technique of on-line coupling ion chromatography and atomic spectrometry for ultra trace analysis in high purity molybdenum and tungsten is extended to include the silicides MoSi(x) and WSi(x). An additionally included matrix elimination step allows an almost interference-free trace analysis in the silicide matrices. Reproducibility and accuracy of the on-line method were checked by comparison with several other methods, such as isotope dilution, radiochemical neutron activation analysis, direct determination by atomic absorption analysis and not at least with glow discharge mass spectrometry. The results show the high potential of the on-line method for reaching detection limits in the pg g(-1) range, but they show also remaining problems with contamination and system calibration.     

Determination of trace impurities in aluminum nitride by direct solid sampling graphite furnace atomic absorption spectrometry

The trace impurities Cr, Cu, Fe, K, Mn, Sb and Zn were determined in powdered aluminum nitride by direct solid sampling graphite furnace atomic absorption spectrometry using a ZEEnit 60 atomic absorption spectrometer. This spectrometer features inverse Zeeman-effect background correction and a variable magnetic field enabling measurements in two sensitivity modes over a concentration range of three orders of magnitude. The measurement sensitivity can be adjusted to the analyte concentration in the sample. The use of chemical modifiers was not necessary. Calibration was carried out by means of calibration curves obtained with aqueous standard solutions. Accuracy was checked mainly by comparison of the results with those obtained by instrumental and radiochemical neutron activation analysis whereby, excluding the results for potassium, no significant differences were found by carrying out the t-test at the significance level 0.05. The limits of detection were between 0.05 ng g⁻¹ (Zn) and 80 ng g⁻¹ (Fe) and the relative standard deviations below 11 %. With the proposed method, up to ten measurement cycles can be carried out in one hour.     

Slurry sampling graphite furnace atomic absorption spectrometry: determination of trace metals in mineral coal

A procedure for lead, cadmium and copper determination in coal samples based on slurry sampling using an atomic absorption spectrometer equipped with a transversely heated graphite tube atomizer is proposed. The slurries were prepared by weighing the samples directly into autosampler cups (5-30 mg) and adding a 1.5 ml aliquot of a diluent mixture of 5% v/v HNO(3), 0.05% Triton X-100 and 10% ethanol. The slurry was homogenized by manual stirring before measurement. Slurry homogenization using ultrasonic agitation was also investigated for comparison. The effect of particle size and the use of different diluent compositions on the slurry preparation were investigated. The temperature programmes were optimized on the basis of pyrolysis and atomization curves. Absorbance characteristics with and without the addition of a palladium-magnesium modifier were compared. The use of 0.05% m/v Pd and 0.03% m/v Mg was found satisfactory for stabilizing Cd and Pb. The calibration was performed with aqueous standards. In addition, a conventional acid digestion procedure was applied to verify the efficiency of the slurry sampling. Better recoveries of the analytes were obtained when the particle size was reduced to <37 mum. Several certified coal reference materials (BCR Nos. 40, 180, and 181) were analyzed, and good agreement was obtained between the results from the proposed slurry sampling method and the certificate values.     

Dispersive liquid-liquid microextraction combined with graphite furnace atomic absorption spectrometry: ultra trace determination of cadmium in water samples

Dispersive liquid-liquid microextraction (DLLME) technique was successfully used as a sample preparation method for graphite furnace atomic absorption spectrometry (GF AAS). In this extraction method, 500 μL methanol (disperser solvent) containing 34 μL carbon tetrachloride (extraction solvent) and 0.00010 g ammonium pyrrolidine dithiocarbamate (chelating agent) was rapidly injected by syringe into the water sample containing cadmium ions (interest analyte). Thereby, a cloudy solution formed. The cloudy state resulted from the formation of fine droplets of carbon tetrachloride, which have been dispersed, in bulk aqueous sample. At this stage, cadmium reacts with ammonium pyrrolidine dithiocarbamate, and therefore, hydrophobic complex forms which is extracted into the fine droplets of carbon tetrachloride. After centrifugation (2 min at 5000 rpm), these droplets were sedimented at the bottom of the conical test tube (25 ± 1 μL). Then a 20 μL of sedimented phase containing enriched analyte was determined by GF AAS.Some effective parameters on extraction and complex formation, such as extraction and disperser solvent type and their volume, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor 125 was obtained from only 5.00 mL of water sample. The calibration graph was linear in the rage of 2-20 ng L⁻¹ with detection limit of 0.6 ng L⁻¹. The relative standard deviation (R.S.D.s) for ten replicate measurements of 20 ng L⁻¹ of cadmium was 3.5%. The relative recoveries of cadmium in tap, sea and rivers water samples at spiking level of 5 and 10 ng L⁻¹ are 108, 95, 87 and 98%, respectively. The characteristics of the proposed method have been compared with cloud point extraction (CPE), on-line liquid-liquid extraction, single drop microextraction (SDME), on-line solid phase extraction (SPE) and co-precipitation based on bibliographic data. Therefore, DLLME combined with GF AAS is a very simple, rapid and sensitive method, which requires low volume of sample (5.00 mL).     

Determination of ultra trace amounts of cobalt in fish by graphite furnace Zeeman effect atomic absorption spectrometry

A method is described for determining stable cobalt concentrations in fish flesh and bone using polarized Zeeman effect graphite furnace atomic absorption spectrometry (ZAAS). Cobalt analysis on freshwater fish flesh samples (10 g dry weight) required predigestion and wet-ashing at 70-80 degrees C. Cobalt is chelated with ammonium pyrrolidine dithiocarbamate (APDC) extracted with methyl isobutyl ketone (MIBK) and analysed by ZAAS. The mean cobalt content calculated from the standard additions method using three replicate fish flesh samples was 4.23 +/- 1.0 microgram Co. Kg-1 (dry weight). Analyses were also carried out on flesh and bone samples from similar sized fish, of the same species, taken from three area lakes.     

Study of some palladium-containing chemical modifiers in graphite furnace atomic absorption spectrometry

Several chemical modifiers based on palladium have been evaluated: the individual Pd(II) and the mixed modifiers Pd + Zr, Pd + W, Pd + Zr + citric acid, Pd + W + citric acid. The mechanisms by which these chemical modifiers stabilize analytes and control atomization have been suggested. Factors that might have an influence on the characteristic mass and non-spectral interferences are discussed. The advantages and limitations of the palladium-tungsten modifiers are shown.     

On-line hyphenation of capillary electrophoresis with flame-heated furnace atomic absorption spectrometry for trace mercury speciation

Capillary electrophoresis (CE) was directly interfaced to flame-heated furnace atomic absorption spectrometry (FHF-AAS) via a laboratory-made thermospray interface for nanoliter trace element speciation. The CE-FHF-AAS interface integrated the superiorities of stable CE separation, complete sample introduction, and continuous vaporization for AAS detection without the need of extra external heat sources and any post-column derivation steps. To demonstrate the usefulness of the developed hybrid technique for speciation analysis, three environmentally significant and toxic forms of methylmercury (MeHg), phenylmercury (PhHg), and inorganic mercury (Hg(II)) were taken as model analytes. Baseline separation of the three mercury species was achieved by CE in a 60 cm long x 75 microm inner diameter fused-silica capillary at 20 kV and using a mixture of 100 mM boric acid and 10% v/v methanol (pH 8.30) as running electrolyte. The precision (relative standard deviation, RSD, n = 7) of migration time, peak area and peak height for the mercury species at 500 microg x L(-1) (as Hg) level were in the range of 0.9-1.2%, 1.5-1.9%, and 1.4-2.0%, respectively. The detection limit (S/N = 3) of three mercury species was 3.0 +/- 0.15 pg (as Hg), corresponding to 50.8 +/- 2.4 microg x L(-1) (as Hg) for 60 nL sample injection, which was almost independent on specific mercury species. The developed hybrid technique was successfully applied to the speciation analysis of mercury in a certified reference material (DORM-2, dogfish muscle).     

石墨炉原子吸收法测定石脑油中微量砷

试样用四氢呋喃（THF）有机溶剂稀释,以硝酸镍为基体改进剂,研究采用石墨炉原子吸收法直接进样测定石脑油中的砷量。研究表明,砷量在0～50μg／L范围内线性关系良好,回收率93％～104％。     

On-line electrochemical preconcentration of manganese for graphite furnace atomic absorption spectrometry using a flow-through electrochemical cell

A flow system incorporating a 2-electrode electrochemical microcell with a working electrode made from crushed reticulated vitreous carbon and a graphite furnace AAS instrument was used for the preconcentration and determination of trace amounts of Mn. The sample, rinsing and elution solutions were pneumatically transported through the system. Mn²⁺ ions can be quantitatively deposited both anodically and cathodically at a voltage of +1.5 to + 3 V and –2.5 to –4V, respectively applied to the cell. Samples of 0.1 to 1 ml volume were analyzed within 5–10 min. The limits of detection and determination were 8.7 and 29 pg, respectively. The reproducibility was 1.5 to 5%. The electrochemical behaviour of Mn in the flow system was studied by using a 3-electrode flow-through cell coupled on-line to a flame AAS instrument.On leave from Department of Analytical Chemistry, Slovak Technical University, CS-812 37 Bratislava, Czechoslovakia     

Collection and preparation of sidestream cigarette smoke for trace elemental determinations by graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry.

A novel method for the collection and preparation of sidestream cigarette smoke condensate is described for trace elemental analysis by inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry. The smoke collection method utilizes a specially designed chimney that collects and directs the sidestream smoke (SS) to a 2-stage trapping system consisting of an impaction trap followed by a 0.8 microm mixed cellulose ester filter. The samples are digested with nitric acid in a commercial heating block before analysis. The method limits of detection (LODs) are 1, 0.2, 2, 9, 6, and 7 ng/cigt for As, Cd, Pb, Ni, Se, and Cr, respectively. The SS collected from an industry reference cigarette, 1R4F, produced by the University of Kentucky was analyzed. The concentrations of As, Cd, and Pb in 1R4F were determined to be 27.3+/-2.1, 412+/-14, and 43.8+/-2.0 ng/cigt, respectively, while the concentrations of Ni, Cr, and Se are below the method LOD. Consequently, this novel method successfully addresses contamination, instrumentation, and collection issues for performing trace elemental analysis of sidestream cigarette smoke condensate.     

石墨炉原子吸收法测定钢中铅的干扰抑制

研究了石墨炉原子化法测定钢铁中痕量铅的干扰情况，并进行了干扰抑制实验。提出了抑制干扰的方法。     

Determination of trace impurities in iron and nickel-base alloys by graphite furnace atomic absorption spectrometry

Five approaches to the determination of trace amounts of lead, bismuth, thallium, selenium, tellurium, and silver in iron and nickel-based alloys were investigated. While all procedures produced satisfactory results, direct techniques yielded a significant times advantage over separation schemes. Matrix effects made calibration curves an impractical approach. A spiking technique was used to generate data on a wide range of standard alloy samples.     

Preconcentration and determination of ultra trace amounts of palladium in water samples by dispersive liquid-liquid microextraction and graphite furnace atomic absorption spectrometry

A highly sensitive, simple and rapid method is presented for the determination of palladium using graphite furnace atomic absorption spectrometry after its separation and preconcentration by dispersive liquid-liquid microextraction. Ultra traces of Pd were extracted and preconcentrated in acidic water samples by using 2-amino-1-cyclohexene-1-dithiocarboxylic acid as a suitable chelating agent, and carbon tetrachloride and acetone as extraction and disperser solvents, respectively. The experimental parameters were optimized in order to enhance the extraction efficiency. After optimizing the extraction conditions and various instrumental parameters, an enhancement factor of 350 was obtained. The analytical curve absorbance vs. concentration was linear over the range 0.02–0.6 µg L^-1 Pd. The detection limit and relative standard deviation were 0.007 µg L^-1 and 4.2%, respectively. The method was successfully applied to the determination of palladium in roadside soil and several aqueous samples.     

Preconcentration of trace heavy metals in water by coprecipitation with magnesium oxinate for electrothermal atomic absorption spectrometry

Nanogram quantities of heavy metals in 200 ml of water were quantitatively preconcentrated by coprecipitation with magnesium oxinate at pH 9–9.5. The precipitate was collected on a 1-m Nuclepore membrane filter and then dissolved in 5 ml of 1 mol/l nitric acid. After diluting to 10 ml with water, a 10- or 20-l aliquot of the solution was directly analyzed by electrothermal atomic absorption spectrometry using deuterium background correction. The background absorption due to the collector magnesium oxinate was negligibly small. The optimized coprecipitation technique has been applied to the determination of cobalt, nickel, copper, cadmium and lead at the ppt level in river and seawater. The relative standard deviations were within 10% and the detection limits were 0.025 (for Co), 0.019 (for Ni), 0.006 (for Cu), 0.001 (for Cd) and 0.017 g/l (for Pb). Blanks through the whole procedure were not detectable.     

A highly sensitive procedure for determination of ultra trace amounts of molybdenum by graphite furnace atomic absorption spectrometry after dispersive liquid-liquid microextraction

A simple, rapid and sensitive method is developed for selective determination of ultra trace amounts of molybdenum(V?) from different water samples. The method is based on highly efficient separation and pre-concentration of molybdenum(V?) by dispersive liquid-liquid microextraction followed by its determination with graphite furnace atomic absorption spectrometry. Ultra traces of the target ion were extracted and pre-concentrated from acidic water samples by using sodium diethyldithiocarbamate as a suitable chelating agent, and carbon tetrachloride and acetone as extraction and disperser solvents, respectively. After optimizing different parameters, including type and volume of extraction and disperser solvents, pH of test solution, extraction time, volume and concentration of the chelating agent and sample volume, an enrichment factor of 362 was obtained. The linear concentration range, limit of detection and relative standard deviation of the method were evaluated as 0.04–0.8 ng mL^?1, 0.007 ng mL^?1 and 4.5%, respectively. This method was applied successfully to the determination of molybdenum in tap water and wastewater samples.     

样品基体化学改进剂-石墨炉原子吸收光谱法测定镍合金中痕量铋

镍基合金是航空工业的重要金属材料,合金中铋、铅、锡等易挥发元素的含量对合金材料性能影响很大[1,2].原子光谱法常被用于分析镍基合金中的痕量元素,如火焰原子吸收光谱法(FAAS)、氢化物发生-原子吸收(荧光)光谱法(HG-AAS/AFS) [3]、电感耦合等离子体-质谱法(ICP-MS).     

石墨炉原子吸收光谱法测定中药漏芦中微量铅

中药漏芦具有抑制动脉粥样硬化、抗脂质过氧化、减弱血小板聚集和提高免疫力等作用[1]。测定中药中微量元素的含量,对于探讨中药药理、提高药效和降低毒副作用有重要的意义[2,3]。铅是一种毒性元素,它在人体中具有累积性,通过肠胃道吸收,严重损害神经系统、造血系统和消化系统,从而导致肌体免疫力降低。本文选用磷酸氢二铵为基体改进剂,采用石墨炉原子吸收光谱法,对漏芦中Pb的含量进行了测定,考察了影响测定结果的主要因素。样品分析结果表明,本法简便、快速、灵敏、准确。1　实验部分1 1　仪器及工作条件180 80型原子吸收分光光度计、…