Analysis of aluminium-based ceramic powders by electrothermal vaporization inductively coupled plasma atomic emission spectrometry using a tungsten coil and slurry sampling

Slurry sampling followed by electrothermal vaporization was used as sample introduction technique for digestion-free analysis of aluminium nitride and aluminium oxide by inductively coupled plasma atomic emission spectrometry. The vaporizer consisted of a tungsten coil in a quartz chamber. Spectral interferences and background emission caused by tungsten ablation from the coil were reduced by coating it with tungsten carbide. Different approaches for background correction techniques were considered. The analytes Ca, Cd, Co, Cr, Cu, Fe, Mg, Ni and Zn were determined simultaneously, whereas Mn and Na were determined in the sequential mode. Calibration was performed using the standard additions method. The accuracy was checked by comparison of the results with those of independent methods. Detection limits between 0.01 (Mg) and 8.5 μg/g (Co) were achieved.     

Solid sampling electrothermal atomic absorption spectrometry for analysis of high-purity tungsten trioxide and high-purity tungsten blue oxide

A solid sampling ETAAS method for the direct determination of Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni and Zn in high-purity tungsten trioxide and tungsten blue oxide powders using a modern spectrometer with transversely heated graphite tube and a solid sampling system is described. The extremely high background caused by the vaporizing tungsten oxides could be eliminated by the reduction to tungsten metal using hydrogen as purge gas during pyrolysis. Quantification of all elements was performed using calibration curves measured with aqueous standard solutions. The analyte contents determined were between 0.033 (Cu) and 12.6 (Fe) μg/g for tungsten trioxide and between 0.001 (Co) and 0.5 (Na) μg/g for tungsten blue oxide. The accuracy was checked by comparing the results with those obtained by ETAAS in analysis of HF/HNO₃ sample digests and by other methods. Extremely low limits of detection being between 0.07 (Mg, Na, Zn) - 2 (Ni) and 0.01 (Mg, Na, Ni) - 1.7 (Fe) ng/g for tungsten trioxide and tungsten blue oxide, respectively, could be achieved due to almost complete freedom of blank and unusually high applicable sample amounts (5–15 mg for tungsten trioxide and 5–70 mg for tungsten blue oxide).     

A new atomization cell for trace metal determinations by tungsten coil atomic spectrometry

A new metallic atomization cell is used for trace metal determinations by tungsten coil atomic absorption spectrometry and tungsten coil atomic emission spectrometry. Different protecting gas mixtures are evaluated to improve atomic emission signals. Ar, N₂, CO₂ and He are used as solvents, and H₂ and C₂H₂ as solutes. A H₂/Ar mixture provided the best results. Parameters such as protecting gas flow rate and atomization current are also optimized. The optimal conditions are used to determine the figures of merit for both methods and the results are compared with values found in the literature. The new cell provides a better control of the radiation reaching the detector and a small, more isothermal environment around the atomizer. A more concentrated atomic cloud and a smaller background signal result in lower limits of detection using both methods. Cu (324.7 nm), Cd (228.8 nm) and Sn (286.3 nm) determined by tungsten coil atomic absorption spectrometry presented limits of detection as low as 0.6, 0.1, and 2.2 μg L⁻¹, respectively. For Cr (425.4 nm), Eu (459.4 nm) and Sr (460.7 nm) determined by tungsten coil atomic emission spectrometry, limits of detection of 4.5, 2.5, and 0.1 μg L⁻¹ were calculated. The method is used to determine Cu, Cd, Cr and Sr in a water standard reference material. Results for Cu, Cd and Cr presented no significant difference from reported values in a 95% confidence level. For Sr, a 113% recovery was obtained.     

Advances with tungsten coil atomizers: Continuum source atomic absorption and emission spectrometry

Two new tungsten coil spectrometers are described: a continuum source tungsten coil atomic absorption spectrometer and a tungsten coil atomic emission spectrometer. Both devices use a 150 W tungsten coil extracted from a slide projector bulb. The power is provided by a computer-controlled, solid state, constant current 0–10 A supply. The heart of the optical system is a high-resolution spectrometer with a multi-channel detector. The continuum source system employs xenon or deuterium lamps, and is capable of multi-element analyses of complex samples like engine oil, urine, and polluted water. Spiked engine oil samples give mean percent recoveries of 98 ± 9, 104 ± 9, and 93 ± 0.8 for Al, V, and Ni, respectively. Copper, Zn, and Cd are determined in urine samples; while Cd, Co, Yb, and Sr are determined in water samples. Detection limits for Cd, Zn, Cu, Yb, Sr, and Co are: 8, 40, 1, 4, 1, and 4 μg l^− 1. The technique of tungsten coil atomic emission spectrometry using a 150 W commercial projector bulb is reported for the first time. Calcium, Ba, and Sr are determined with detection limits of 0.01, 0.5, and 0.1 μg l^− 1. Relative standard deviations are lower than 10% in each case, and Sr is determined in two water standard reference materials.     

Slurry sampling electrothermal atomic absorption spectrometry for trace element analysis of high-purity tungsten trioxide

A slurry sampling ETAAS method for the determination of trace concentrations of Ca, Co, Cr, Cu, Fe, K, Mg, Na and Ni in tungsten trioxide is presented. A high background absorption appearing with large sample amounts during atomization at high temperatures was the only matrix interference observed. It could be significantly reduced by volatilization of the matrix in the pyrolysis step. Calibration curves recorded with aqueous standards could be used for calibration in all cases excluding the determination of very low analyte concentrations of Co and Fe which required the use of the standard additions method. The results obtained by this method showed an excellent agreement with those determined in digests by ETAAS. The detection limits achievable by the slurry technique were between 1 (Ca, K, Mg, Na) and 210 (Cu) ng/g. They were mostly by more than one order of magnitude better than those of the solution techniques. Received: 9 July 1997 / Revised: 6 October 1997 / Accepted: 10 October 1997     

Tungsten coil atomic emission spectrometry

A tungsten coil atomic emission spectrometer is described and evaluated. The system employs a single tungsten coil as a combined atomizer and excitation source for the determination of metals by atomic emission spectrometry. The tungsten coil is extracted from a 150 W, 15 V commercial slide projector light bulb. A simple, laboratory constructed, computer-controlled power supply provides a constant current to the coil. A high-resolution Czerny–Turner monochromator with a charge coupled device detector completes the system. Simultaneous, multi-element analyses are possible within a 4 nm spectral window. Eleven test elements are used to characterize the system: Al (396.1 nm), Co (353.0 nm), Cr (427.1 nm), Dy (404.6 nm), Ga (403.3 nm), K (404.4 nm), Mn (403.1 nm), Pb (405.8 nm), Rb (420.2 nm), Sc (404.8 nm), and Yb (398.7 nm). Tungsten coil atomic emission detection limits are reported for these elements for the first time: 0.02 ng Al, 0.7 ng Co, 0.003 ng Cr, 0.01 ng Dy, 0.7 ng Ga, 0.3 ng K, 0.04 ng Mn, 10 ng Pb, 0.07 ng Rb, 1 ng Sc, and 0.003 ng Yb. The precision for the new technique is better than 13% relative standard deviation for all metals at concentrations two orders of magnitude above the detection limit. Aluminum, Cr, Mn, and K are determined in a standard reference material (trace elements in water) after simple dilution with water, and found values varied from certified values by up to 26%. The average tungsten coil lifetime was found to be 265 heating cycles. The elimination of the external radiation source needed for atomic absorption measurements results in an emission system that could be quite portable.     

Slurry sampling electrothermal atomic absorption spectrometry for trace element analysis of high-purity tungsten trioxide

A slurry sampling ETAAS method for the determination of trace concentrations of Ca, Co, Cr, Cu, Fe, K, Mg, Na and Ni in tungsten trioxide is presented. A high background absorption appearing with large sample amounts during atomization at high temperatures was the only matrix interference observed. It could be significantly reduced by volatilization of the matrix in the pyrolysis step. Calibration curves recorded with aqueous standards could be used for calibration in all cases excluding the determination of very low analyte concentrations of Co and Fe which required the use of the standard additions method. The results obtained by this method showed an excellent agreement with those determined in digests by ETAAS. The detection limits achievable by the slurry technique were between 1 (Ca, K, Mg, Na) and 210 (Cu) ng/g. They were mostly by more than one order of magnitude better than those of the solution techniques.     

Study of chemical modifiers for the determination of chromium in biological materials by tungsten coil electrothermal atomic absorption spectrometry

The determination of Cr in digest solutions of mussels and non-fat milk powder by tungsten coil electrothermal atomic absorption spectrophotometry (TC-ETAAS) is affected by interferences. This study reports a critical evaluation of chemical modifiers that could be employed to correct these interferences. The chemical modifiers tested were: Mg [as Mg(NO₃)₂], Pd [as Pd(NO₃)₂], NH₄NO₃, ascorbic acid, and mixtures of these compounds. The less effective modifier was NH₄NO₃. The best effects, considering thermal stabilization and sensitivity, were obtained in mixtures of ascorbic acid plus Mg. Chromium was determined by TC-ETAAS in certified reference materials of mussels and non-fat milk powder, and results were comparable with those obtained by graphite furnace atomic absorption spectrophotometry (GFAAS). Received: 19 June 1998 / Revised: 11 January 1999 / Accepted: 16 January 1999     

Direct determination of trace elements in tungsten products using an inductively coupled plasma optical emission charge coupled device detector spectrometer

An echelle inductively coupled plasma optical emission spectrometer equipped with a segmented array of charge coupled device detectors was used for the direct determination of trace impurities in tungsten products. No sample preparation was necessary. The multicomponent spectral fitting software provided by the instrument was used for the correction of spectral interference and background. The detection limits of the trace elements Al, As, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Ni, P, Pb, Sb, Sn, Ti and V in tungsten matrix were obtained under optimized operating conditions. The accuracy of the proposed method was assessed using three National Reference Materials. As a result of their ultra-trace concentrations in the reference materials, As, Pb and Sn could not be determined satisfactorily. The concentrations found for the other elements agreed quite well with those of the certified values of the reference materials.     

Electrothermal behavior of sodium,potassium, calcium and magnesium in a tungsten coil atomizer and review of interfering effects

The electrothermal behavior of Na, K, Ca and Mg in a 150-W tungsten coil atomizer was investigated in order to gather information about the atomization processes and the underlying factors responsible for chemical interferences of them on atomization of Al, Ba, Cd, Co, Cr, Pb and Yb. The interference effects were discussed considering the thermal stability of the species that could be formed in the condensed phase, the effect of protective gas composition in the atomization process and the pyrolysis temperature curves. Ca is the most serious interferent due to its high thermal stability (up to 1600°C) and to the possibility of double oxides formation. As hydrogen is decisive for the atomization of Na, K, Ca and Mg, some interference processes caused by these elements seem to be related to the competition towards hydrogen present in the protective gas composition. The knowledge of the correct temperature of the tungsten coil surface shows that most strategies for overcoming interferences based on chemical modifiers will fail for Cd and Pb, because tungsten acts as a natural permanent chemical modifier. It seems that in many applications previous separation and masking will be necessary.     

Determination of aluminium in AlCl3 and Al2O3 modified silica catalyst supports

X-ray fluorescence spectrometry (XRF) was applied to determine aluminium in AlCl₃- and Al₂O₃-modified silica catalyst supports that were prepared by gas-solid reactions in an atomic layer epitaxy (ALE) process using aluminium chloride or aluminium chloride and water as adsorbates and silica as support. INAA and AAS were used as reference methods to determine the aluminium content of the supports. The calibration of XRF results was done by plotting the Al/Si intensity ratios against the aluminium content as determined by atomic absorption spectrometry (AAS) and verified by instrumental neutron activation analysis (INAA). Correlation factors for the calibration graphs were 0.984 for AlCl₃/SiO₂ and 0.995 for Al₂O₃/ SiO₂ samples in the aluminium content range 0–2.6 g Al per 100 g of sample. Received: 19 October 1998 / Accepted: 14 December 1998     

Determination of aluminium in AlCl3 and Al2O3 modified silica catalyst supports

X-ray fluorescence spectrometry (XRF) was applied to determine aluminium in AlCl₃- and Al₂O₃-modified silica catalyst supports that were prepared by gas-solid reactions in an atomic layer epitaxy (ALE) process using aluminium chloride or aluminium chloride and water as adsorbates and silica as support. INAA and AAS were used as reference methods to determine the aluminium content of the supports. The calibration of XRF results was done by plotting the Al/Si intensity ratios against the aluminium content as determined by atomic absorption spectrometry (AAS) and verified by instrumental neutron activation analysis (INAA). Correlation factors for the calibration graphs were 0.984 for AlCl₃/SiO₂ and 0.995 for Al₂O₃/ SiO₂ samples in the aluminium content range 0–2.6 g Al per 100 g of sample. Received: 19 October 1998 / Accepted: 14 December 1998     

Determination of Manganese in Sludge,Alloy, and Soil by Tungsten Coil Atomic Emission Spectrometry

A tungsten coil atomic emission spectrometer (WCAES) was developed and evaluated for the determination of manganese in industrial sludge, alloy, and soil. The system employed a coil extracted from a 150 watts/15 volts commercial slide projector light bulb and a simple power supply that provided a constant current to the coil. The analytical signals were resolved and detected using a Czerny-Turner spectrometer and a charge coupled device. Three manganese emission lines were detected simultaneously. Using different emission lines, limits of detection for manganese varied from 0.54 to 0.65 milligram per liter, and relative standard deviations for manganese at 5 milligrams per liter varied from 5.9 to 8.5 percent (n = 10). Summation of the Mn signals improved the detection limit to 0.17 milligram per liter and decreased the relative standard deviation to 1.7 percent. Spectral interferences were observed in the presence of Al, Ca, K, and Na. The accuracy was determined using two certified reference materials, and the results obtained by WCAES were in agreement with those obtained by inductively coupled plasma-optical emission spectrometry at the 95 percent confidence level.     

Determination of cadmium and lead in mussels by tungsten coil electrothermal atomic absorption spectrometry

In this work it was evaluated the determination of Cd and Pb in mussels by tungsten coil electrothermal atomic absorption spectrometry (TCA-AAS). A critical and comprehensive study of the effects caused by Pd, Mg, ascorbic acid, and binary mixtures of these compounds on the atomization of Cd and Pb in acid digested solutions of mussels was performed. Palladium and mixtures containing it were useful to increase sensitivity and thermal stability of Cd and Pb. Additionally, the coil lifetime was increased and the background signals were decreased in these modifiers. All these favorable effects were analytically exploited to determine Cd and Pb in samples of mussels. The proposed methodology was validated using two certified reference materials (oyster tissue and mussel). No statistical difference was observed between determined and certified values at a 95% confidence level. Cadmium and Pb in Chilean bivalve mussels were determined by TCA and by graphite furnace-AAS. Again, the results showed statistical agreement.     

共沉淀分离富集-电感耦合等离子体原子发射光谱法测定高纯氧化钨中痕量金属杂质

提出了以Ｌａ（ＯＨ）３为共沉淀剂，对高纯氧化钨中的痕量金属杂质元素经共沉淀预分离富集后进行ＩＣＰ－ＡＥＳ测定的分析方法。探讨了影响杂质元素回收率和钨残留量的若干因素，确定了合适的分离富集条件。合成试样和标准样品的测试结果表明： Ｂｉ、Ｃａ、Ｃｄ、Ｃｏ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎｉ、Ｐｂ、Ｓｂ、Ｓｎ、Ｔｉ等元素能被定量分离回收，回收率和精密度均令人满意。     

电沉积-钨丝电热原子吸收光谱法测定水样中的铅

研制了一种便携式钨丝电热原子吸收光谱分析装置,其主要包括:钨丝电热原子化器、多道微型CCD光谱仪、仪器电源系统以及控制系统。并将电沉积分离富集技术与该钨丝电热原子吸收光谱分析仪器结合,完成环境水样中铅的现场分析。并对铅的电沉积条件作了研究,最佳电沉积电位为负650 mV(vs.SCE),方法检出限:0.20μg/L,线性范围:1~15μg/L,对4μg/L Pb标准溶液10次重复测试,RSD为4.4%。     

Determination of trace inpurities high-purity aluminum oxide by inductively-coupled plasma atomic emission-spectrometry

Trace impurities (Ca, Cu, Fe, Mg, Mn, Na and Si) in 99.99% aluminum oxide were determined by inductively-coupled plasma atomic emission spectrometry (i.c.p./a.e.s.). The sample was fused with lithium carbonate/boric acid to determine Ca, Cu, Mg, Mn, Na and Si or dissolved in phosphoric/sulphuric acids to determine iron. Matrix effects on the calibration graphs for each element were studied: for accurate determinations, calibration solutions must contain lithium and boric acid (or aluminium and phosphoric and sulphuric acids for iron).     

Characterization of the chemical composition of archaeological glass finds from South-Eastern Bulgaria using PIXE, PIGE and ICP-AES

Using PIXE (proton induced X-ray emission), PIGE (proton induced gamma emission) and ICP-AES (inductively coupled plasma-atomic emission spectroscopy) the concentrations of the 24 elements Al, As, Ba, Br, Ca, Cl, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, Rb, S, Sb, Si, Sn, Sr, Ti, Zn and Zr in 53 archaeological glass samples from South-Eastern Bulgaria, were determined. The glasses are dated from the 1st to 6th century AD. The analytical data showed the samples to be typical soda-lime-silica glass, with natron as flux. A rather broad range of aluminium, titanium and iron impurities was found, with a tendency for more impure glass in the later periods. The decolouring agents were antimony and manganese oxides, with Sb prevailing in earlier, and Mn in later glass.     

Determination of lead in blood by tungsten coil electrothermal atomic absorption spectrometry

A method for the determination of lead in blood using a tungsten coil atomizer is described. A 100 μl volume of the whole blood sample is transferred to a sampler cup containing 100 μl of water plus 300 μl of 0.25% v/v Triton X-100. After lysis of blood cells, 500 μl of 10% w/v trichloroacetic acid is added for protein precipitation and 10 μl of the supernatant solution is automatically delivered into the tungsten coil. The furnace heating program is implemented in 41 s. It is shown by the paired t-test that there is no significant difference at the 5% probability level between results obtained by the proposed method and by using a transversely heated graphite atomizer with a longitudinal Zeeman background correction. Accuracy is also assessed by employing reference materials. The proposed tungsten coil procedure presents a characteristic mass of 15 pg Pb and a detection limit of 1.9 μg Pb dl⁻¹.