Electrothermal vaporization-ICP-MS for the determination of metals in micro amounts of high-purity non-metals (P, As, Sb, S, Se, Te, I)

A thermal trace-matrix separation procedure has been developed for the determination of ultra-traces of metals in solid non-metals (P, As, Sb, S, Se, Te and I). These matrices are dissolved in high-purity hydrogen peroxide to form the corresponding acids. By applying a suitable temperature profile, coating the graphite tube with WC and using hydrogen as a gaseous modifier more than 90% of the matrix can be removed. Analyte recoveries are 90 to 105% with a standard deviation of 5 to 10%. Since the separation principle is not specific, non-metallic analytes show poor recoveries of 10 to 40% (20–100% RSD). Elements forming persistent carbides, such as refractory metals, require either HF or freon as an additional modifier. Separation of the matrix leads to higher sensitivities, fewer spectral and non-spectral interferences and to better precision. The graphite tube is only little contaminated and its lifetime is drastically increased. The improvements result in limits of detection in the lower pg/g-range in the solid non-metals. Furthermore, this method can be employed for amounts of sample around 1 mg at absolute detection limits below 1 pg. Best performance of the coupling of ETV to ICP-MS is only obtained in the single-ion monitoring mode which means only semi-sequential multi-element capabilities.     

Direct determination of boron in a cobalt-based alloy by graphite furnace-atomic absorption spectrometry

A matrix modifier composed of nickel and zirconium, and a graphite tube treated with zirconium solution were proposed for the determination of boron in cobalt-based alloys by graphite furnace-atomic absorption spectrometry. The effects of this matrix modifier and the treated graphite tube were studied, and the combination of 60 mug of nickel and 20 mug of zirconium as matrix modifier, and a graphite tube soaked with 10 g 1(-1) of zirconium solution were found to give the highest analytical sensitivity. The interference effects of major components (cobalt) and eight minor components (chromium, nickel, tungsten, iron, tantalum, molybdenum, titanium, aluminium and manganese) were studied. Boron in four cobalt-based alloys was determined by graphite furnace-atomic absorption spectrometry employing the proposed matrix modifier and the treated graphite tube, without the preseparation of matrix. The relative standard deviation was 3.3% for 0.048% of boron. A characteristic mass was 500 pg.     

Development of methodologies to determine aluminum, cadmium, chromium and lead in drinking water by ET AAS using permanent modifiers

In this work, methodologies were developed to determine aluminum (Al), cadmium chromium and lead in drinking water by electrothermal atomic absorption spectrometry using permanent modifiers. No use of modifier, iridium, ruthenium, rhodium and zirconium (independently, 500 μg) were tested to each one analyte through the pyrolysis and atomization temperatures curves. As the matrix is very simple, did not had occurred problems with the background for all metals. The best results obtained for cadmium and chromium was with the use of rhodium permanent modifier. For lead and aluminum, the best choice was the use of zirconium. The selection for the modifier took into account the sensitivity, form of the absorption pulse and low atomization temperature (what contributes to elevate the useful life of the graphite tube). For aluminum using zirconium permanent, the best pyrolysis and atomization temperatures were respectively, of 1000 and 2500 °C with a characteristic mass (1% of absorbance, m_o) of 19 pg (recommended of 20 pg). For cadmium, with use of rhodium the best temperatures for the pyrolysis and atomization were respectively of 400 and 1100 °C, with a symmetrical peak and with a m_o of 1.0 pg (recommended of 1.0 pg). For chromium with rhodium permanent, the best temperatures for pyrolysis and atomization were respectively of 1000 and 2200 °C, with symmetrical peak and m_o of 5.3 pg (recommended of 5.5 pg). For lead with zirconium permanent, the best temperatures for pyrolysis and atomization were of 700 and 2400 °C, with symmetrical peak and with m_o of 30 pg (recommended of 20 pg). Water samples spiked with each one of the metals in four different levels inside of the acceptable values presented recoveries always close to 100%. The detection limits were of 0.1 μg l⁻¹ for cadmium; 0.2 μg l⁻¹ for chromium; 0.5 μg l⁻¹ for lead and 1.4 μg l⁻¹ for aluminum.     

Fluorination assisted slurry electrothermal vaporization in ICP-AES for the direct analysis of silicon dioxide powder

The performance of palladium as permanent chemical modifier electroplated on the surface of a graphite tube for the preconcentration of antimony hydride was examined and compared with thermally formed Pd-coatings. The application of Pd-electroplated tubes allows to perform at least 75 determination cycles without any significant change in the efficiency of hydride collection. This is an advantage over the thermally formed palladium coating which must be obtained individually before each measurement. After the optimization of the system parameters a concentration detection limit of 48 ng/L and an absolute detection limit of 71 pg for a 1.48 mL sample were obtained. The procedure was applied to the determination of antimony at a concentration level of 0.2 μg/L in a tap water sample. Received: 13 October 1997 / Revised: 8 December 1997 / Accepted: 11 December 1997     

石墨炉原子吸收法测定钒的研究

本文比较了在标准石墨管,热解涂层和全热解石墨管中钒的吸收信号形状。用全热解石墨管和EDTA铵盐作基体改进剂,直接测定水系沉积物中痕量钒。方法的特征量为61pg/0.0044A。     

钯作基体改进剂FIA－HG－GFAAS法测定锗及其机理研究

采用钯，钯－镁作基体改进剂，ＦＩＡ－ＨＧ－ＧＦＡＡＳ法成功地测定了锗。灵敏度、精密度和分析速度都得到很大的提高。峰值吸收的特征质量８．０ｐｇ，检出限１０．９ｐｇ，相对标准偏差０．３４％，同时探讨了基体改进剂钯的稳定作用机理及锗在石墨管中的原子化机理。     

Determination of Fluorine, Chlorine, and Bromine by Molecular Absorption Spectrometry

Fluorine was determined by molecular absorption spectrometry (MAS) in a graphite tube furnace, and fluorine, chlorine, and bromine were determined in a flame. For the fluorine work, aluminum nitrate was added as a reagent to produce aluminum fluoride molecules whose absorbance was monitored with emission from a platinum hollow cathode lamp (HCL) at 227.45 nm. A deuterium arc lamp was employed for background correction. For the furnace work, barium nitrate was used as a chemical modifier to increase the absorption signal. After optimization of the chemical and furnace conditions, a detection limit of 160 pg F was obtained, with a linear dynamic range of two orders of magnitude. Graphite furnace MAS was used to accurately determine fluoride in dental rinse and National Institute of Standards and Technology oyster tissue, but the precision was between 21 and 23%. Low recoveries were obtained for the determination of trifluoroacetic acid and l,2,2,3-tetrafluoropropan-1-ol by graphite furnace MAS. The detection limit for F by flame MAS was 13 mg liter⁻¹ which is a factor of 5 lower than the best reported flame MAS detection limit. Chlorine was determined by flame MAS with the aluminum chloride molecule. Excitation was done at 261.4 nm with a lead HCL. and a detection limit of 180mg liter⁻¹ was obtained. Flame MAS of bromine was done by use of AlBr (excitation at 279.0 nm with an arsenic HCL) and InBr (excitation at 284.3 nm with a chromium HCL), but very poor detection limits were obtained: 24.5 g liter⁻¹ and 500mg liter⁻¹, respectively.     

Determination of Antimony in Environmental Samples by ETAAS Using Different Permanent Modifiers

Single noble metal permanent modifiers such as, Rh, Ir, and Ru, as well as mixed tungsten plus noble metal (W–Rh, W–Ru, W–Ir) permanent modifiers thermally deposited on the integrated platform of a transversally heated graphite atomizer (TGA) were employed for the determination of antimony in sludge, soil, sediment, coal, ash and water samples by electrothermal atomic absorption spectrometry (ETAAS).Microwave digests of solid samples and water samples were directly introduced into different pre-treated platforms of graphite tubes. The performance of the modifiers for accurate antimony determination in real samples depended strongly on the type of permanent modifier chosen. The single noble metal (Rh, Ir and Ru) permanent modifiers were suitable for analyte determinations in simpler matrices, such as waters (recoveries of certified values 95–105%), but the analyte recoveries of certified values in sludge, soil, sediment, coal, and ash samples were always lower than 90%. On the other hand, for the determination of antimony, using W–Rh, W–Ru, and W–Ir permanent modifiers presented recoveries of certified values within 95–105% for all the samples.Long-term stability curves obtained for the determination of antimony in environmental samples with different permanent modifiers (Rh, Ir, Ru, W–Rh, W–Ir, W–Ru) showed that the improvement in tube lifetime depends on the tungsten deposit onto the platform. The tungsten plus noble metal permanent modifier presents a tube lifetime of at least 40% longer compared to a single permanent modifier.     

Determination of cadmium, chromium, copper and lead in sediments and soil samples by electrothermal atomic absorption spectrometry using zirconium containing chemical modifiers.

A method for direct determination of cadmium, chromium, copper and lead in sediments and soil samples by electrothermal atomic absorption spectrometry using Zr, Ir, etylenediamine acetic acid (EDTA), Zr + EDTA, Ir + EDTA, Zr + Ir and Zr + Ir + EDTA as chemical modifiers in 0.5% (v/v) Triton X-100 plus 0.2% (v/v) nitric acid mixture used as diluent was developed. The effects of mass and mass ratio of modifiers on analytes in sample solutions were studied. The optimum masses and mass ratios of modifiers: 20 microg of Zr, 4 microg of Ir, 100 microg of EDTA and 20 microg of Zr + 4 microg of Ir + 100 microg of EDTA, were used to enhance the analyte signals. Pyrolysis and atomization temperatures, atomization and background absorption profiles, characteristic masses, and detection limits of analytes in samples were compared in the presence or absence of a modifier. The detection limits and characteristic masses of analytes in a 0.5% (m/v) dissolved sample (dilution factor of 200 ml g(-1)) obtained with Zr + Ir + EDTA are 8.0 ng g(-1) and 1.2 pg for Cd, 61 ng g(-1) and 4.3 pg for Cr, 32 ng g(-1) and 23 pg for Cu, and 3.4 ng g(-1) and 19 pg for Pb, respectively. The Zr + Ir + EDTA modifier mixture was found to be preferable for the determination of analytes in sediment and soil-certified and standard reference materials. Depending on the sample type, the percent recoveries of analytes were increased from 81 to 103% by using the proposed modifier mixture; the results obtained are in good agreement with the certified values.     

石墨炉原子吸收分光光度法测定固体废物中铍和钼

建立了石墨炉原子吸收法测定固体废物中铍和钼的方法。采用盐酸–硝酸–氢氟酸–高氯酸消解样品,钯盐作基体改进剂,消除了基体干扰。铍、钼的质量浓度分别在0~4.0,0~50.0μg/L范围内与吸光度呈良好的线性,线性相关系数均为0.999 6,检出限分别为0.03,0.2μg/g。实际样品加标回收率为82.5%~117.0%,测定结果的相对标准偏差为6.6%~10.4%(n=6)。该方法选择性强、灵敏度高,测定结果准确,满足固体废物全量分析要求。     

Bestimmung von Elementspuren im ng- und pg-Bereich durch optische Emissionsspektrometrie mit He-MIP-Anregung nach elektrolytischer Abtrennung im Graphitrohr und nach-folgender elektrothermischer Atomisierung

This article deals with the determination of traces of elements in the ng and pg range by emission spectroscopy with a He-MIP excitation after electrolytic preconcentration in a graphit tube followed by electrothermal atomization. A multi-stage combined procedure is described for the sensitive and reliable determination of trace elements in high-purity metals. Electrolytically depositable elements such as noble metals, copper, as well as bismuth, cadmium, iron, cobalt, zinc, and others are preconcentrated from acidic solutions with concentrations ? 0.05 ng ml^?1 after the decomposition of the sample if the matrix elements are not deposited. The electrolyte is cycled through a small cylindrical cathode of pure graphite on the inner wall of which the elements are deposited. The graphite tube is coupled directly to the quartz capillary of a microwave induced helium plasma (MIP). After electrothermal atomisation the trace elements are determined by emission spectrometry. Different types of MIP excitation sources are investigated. The MIP with the TM₀₁₀ microwave resonator shows optimal properties. For the determination of the trace elements in niobium and beryllium detection limits near 1 ng g^?1 and relative standard deviations between 6.5 and 15% are obtained.     

石墨炉原子吸收法直接测定全血中镉和铅

直接测定人体血镉和血铅较为困难。本文介绍用铂作基体改进剂以提高镉、铅的灰化温度,在灰化阶段除去产生高背景吸收的蛋白,而不发生镉、铅的挥发损失。实现了不需消化样品、络合提取等复杂的化学前处理,用石墨炉原子吸收法和校正曲线直接测定。同时应用衬钽技术,大大延长了石墨管的使用寿命。     

Cloud point extraction of trace metals from seawater and determination by electrothermal atomic absorption spectrometry with iridium permanent modifier.

A simple method is described for preconcentration and separation of trace metals such as Ag, Co, Cr, Cu, Fe, Mn, Ni and Pb simultaneously from seawater using a cloud point extraction (CPE) procedure. Triton X-114 nonionic surfactant and ammonium pyrrolidine dithiocarbamate (APDC) have been used as an extraction medium and a chelating extractant, respectively. The amounts of Triton X-114 and APDC and the pH value necessary for extraction were carefully optimized. The preconcentration factor of about 200 is achieved for all the studied metals. Electrothermal atomic absorption spectrometry (ETAAS) with an Ir coated graphite tube as permanent chemical modifier has been used for determination. The limits of detection of Ag, Co, Cr, Cu, Fe, Mn, Ni and Pb were 0.003, 0.008, 0.003, 0.006, 0.015, 0.002, 0.009 and 0.01 ng ml-1, respectively. Certified reference materials such as CASS-4 and NASS-5 (seawater) and NIST-1640 (natural water) have been used for validation of the new method. The relative standard deviation (%) obtained for all the metals are in the range 0.8 - 3.6% for natural water and 11-25% for seawater materials, except for Co in NASS-5 for which it was 50%.     

Determination of As, Cd, and Pb in epicuticular waxes of pine and spruce needles by ETAAS

 Waxes were separated from needles by chloroform washing, drying and dissolving the residue in tetrahydrofuran (THF). Both a THF solution of the wax and an aqueous solution of the Pd-Mg matrix modifier were sampled directly into the graphite tube. The reaction conditions were optimised for the wax concentration of 45 mg ml^-1 in THF and the Pd:Mg ratio of 1:1 in the matrix modifier. The atomisation and charring temperatures for As, Cd and Pb were the same as those recommended for analysis of aqueous solutions except the charring temperature of Cd takes 200 °C lower. The characteristic masses for As (26 pg), Cd (0.5 pg) and pb (9 pg) are also comparable to published data. The parameters of calibration curves were identical for all three elements dissolved either in clear THF or in the wax solution. Elemental concentrations were found to range from 0.1 to 1.0 mg g^-1, increasing with needle age for As, Pb but not Cd. Received: 20 September 1996 / Revised: 14 November 1996 / Accepted: 13 December 1996     

微波消解石墨炉原子吸收法测定人发中的铅、镉

采用石墨炉原子吸收分光光度法(GFAAS)测定人发中的铅、镉含量.采用微波消解法消解样品,加入(NH4)2SO4+KH2PO4基体改进剂消除干扰,对消化剂种类、消解压力、仪器条件等进行了探索.方法简便、准确度高,Pb和Cd的平均回收率分别为101.8%和107.1%,相对标准偏差(RSD)为5.14%和6.80%,方法检出限Pb为9.53 ng/mL,Cd为0.78 ng/mL.     

Determination of tributyltin in toluene extract from sea water by graphite furnace atomic absorption spectrometry with a new matrix modifier

A new matrix modifier composed of calcium and chromium[VI] was proposed for the determination of tributyltin (TBT) in toluene extract from sea water containing sediment by graphite furnace atomic absorption spectrometry (GFAAS). Fourteen inorganic and organic compounds (barium, calcium, chromium[VI], lanthanum, magnesium, nickel, palladium, strontium, calcium-chromium[VI], calcium-strontium, nickel isocaprylate, 5%-, 10%-aqueous solution of ascorbic acid and toluene-saturated solution of ascorbic acid) as a matrix modifier were comparatively studied and a matrix modifier composed from 5 microg of calcium and 1 microg of chromium[VI] was found to give the best performance. The interference effects of co-existing elements in sea water containing sediment (aluminium, iron, magnesium, sodium and strontium) were studied. TBT in eight toluene extracts was determined by GFAAS with the proposed matrix modifier. The relative standard deviation was 3.0% for 63 ng ml(-1) of TBT (n = 11). The recoveries were 88-104%. The characteristic mass was 7 pg. The linearity range was 0-250 ng mg(-1).     

Determination of Lead in Human Hair by High Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry with Microwave Digestion and Solid Sampling

The content of lead in human hair was measured by high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) combined with microwave-assisted digestion (MAD) and direct solid sampling (DSS). Hair strands were washed, dried, and then cut into three parts (root, middle portion, and tip). For MAD-GFAAS assays, approximately 0.25 g of hair was completely digested using a mixture of concentrated nitric acid and hydrogen peroxide in a closed system. In the DSS-GFAAS assays, 0.1–0.2 mg of dried hair was directly introduced into a graphite furnace using a solid autosampler. The temperature programs were optimized and the effects of various added modifiers were compared. The results indicated that NH₄H₂PO₄ was the optimal modifier for analysis of Pb using GFAAS. Use of the optimal modifier and temperature program gave similar limits of detection for MAD-GFAAS and DSS-GFAAS of 1.16 ng/g and 0.82 ng/g, respectively. Both methods also produced satisfactory recoveries ranging from 98.69% to 103.14%. There was no significant difference observed between the Pb contents of hair strands determined by the MAD-GFAAS and DSS-GFAAS assays, which both indicated that the Pb levels increased along the hair strands. Comparison of the two methods revealed that DSS-GFAAS had several advantageous characteristics over MAD-GFAAS, including the need for much less sample material and having a less time-consuming procedure, lower sample blank absorbance, lower memory effect, and no risk of environmental pollution by digesting chemicals. The direct solid sampling technique can be employed as a good alternative to conventional wet digestion in AAS assays.     

Inductively Coupled Plasma Mass Spectrometry for Sequential Determination of Trace Metals in Rain and River Waters Using Electrothermal Vaporization

Abstract

The sequential determination of 14 trace metals, Al, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Mo, Cd, Sb and Pb, in rain and river water samples has been investigated using an inductively coupled plasma mass spectrometry (ICP-MS) with a graphite rod electrothermal vaporizer (ETV) in the presence of the mixed modifier of palladium nitrate and magnesium nitrate. The sensitivity enhancements due to the presence of the modifier were observed for all analyte elements. Detection limits as high as 0.52, 0.13, 0.89, 0.35, 1.76, 0.5, 0.9, 0.5, 0.04, 1.03, 0.28, 0.07, 0.1 and 3.78 pg, respectively, for Al, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Mo, Cd, Sb and Pb have been achieved. For the determination of trace metals in both rain and river water samples by this method, the repeatibility of sample solution were very good, i.e. from 1% to 7% (as a coefficient variation) and the recoveries of elements were good enough, i.e. from 81% to 106%, by using a standard addition method. There was no difference between the results obtained by nebulizer ICP-MS and those obtained by this method, except for zinc and arsenic.     

Determination of mercury in mineral coal using cold vapor generation directly from slurries,trapping in a graphite tube,and electrothermal atomization

A rugged and reliable method for the determination of mercury in coal without sample digestion, based on chemical vapor generation (cold vapor technique) from slurried coal samples has been developed. It involves collection of the mercury vapor in a graphite tube, treated with gold or rhodium as permanent modifier, and determination by electrothermal atomic absorption spectrometry. Mercury quantitatively leached out of the investigated coal reference materials into 1 mol l⁻¹ nitric acid within 48 h when the coal was ground to a particle size of ≤50 μm, except for one sample (BCR 180), which had to be ground to ≤30 μm, or a leaching time of 72 h had to be used. No detectable quantity of mercury was generated directly from the slurry particles, but it was not necessary to filter the solution. The greatest advantage of the method is that only a minimum of reagents and sample handling steps are required, a prerequisite for accurate results in routine analysis. The results were well within the 95% confidence level of the certificate or close to the information value of the reference materials investigated. The characteristic mass of 110 pg obtained with gold as the permanent modifier is close to values reported for direct analysis of solutions, showing close to 100% trapping efficiency for mercury. A limit of detection (LOD) of 90 pg absolute was obtained with this modifier, which corresponds to an LOD of 0.009 μg g⁻¹ Hg in coal. This is based on 1 ml of slurry containing 10 mg of coal, and is an order of magnitude lower than the lowest mercury content in the investigated reference materials.     

A temperature-controlled graphite tube furnace for the determination of trace metals in solid biological tissue

A temperature-controlled graphite furnace for atomic-absorption analysis has been built and tested. The temperature of the graphite tube was monitored with an infrared-sensitive detector. Samples were introduced directly or via a separately heated graphite cup. Micro-samples of solid biological tissue were analysed directly for Zn, Mn and Co and the sensitivities for 1% absorption were 0.05,2 and 10 pg respectively. The salt content of the tissue limits the sample sizes, owing to non-specific absorption. The ashing conditions were investigated and found to be especially critical for Zn.