Direct analysis of tantalum powders by electrothermal vaporization inductively coupled plasma atomic emission spectrometry

A direct inductively coupled plasma atomic emission method for the determination of Ag, Al, As, Ca, Cd, Co, Cu, Fe, Ga, K, Li, Mg, Na and Pb in high-purity tantalum powders has been developed. The electrothermal vaporization technique using a modified longitudinally-heated Grün-ETAAS furnace with sample introduction on a platform and an automated sampling workstation provided the possibility of in situ analyte-matrix separation, freedom of blank, and applicability to routine analysis. Hard- and software were modified to allow signal recording and data processing independent of the spectrometer software. The extent of spectral interferences by Ta-emission at the analyte wavelengths used was determined and the analyte signals of each sample run were automatically corrected. Limits of detection ranging from 5 ng/g (Ag, Cu) to 250 ng/g (K, Pb) were obtained using optimized furnace and spectrometer conditions. The method was applied to the analysis of two tantalum samples and the results for Cu, Fe, K, Mg and Na were compared with those obtained by liquid and solid-samping ETAAS, showing satisfactory agreement.     

Determination of aluminum and silicon in biological materials by inductively coupled plasma atomic emission spectrometry with electrothermal vaporization

An atomic emission spectrometric method is described for the determination of trace elements in microvolume samples especially of biological materials. Based upon the arrangement of a commercial electrothermal vaporizer and a 40-MHz inductively coupled plasma, the direct determination of aluminum and silicon in human body fluids such as urine and serum and aluminum in hemodialysis solution is performed. The instrumental system involves vaporizing the sample from a modified graphite electrode followed by atomization and excitation of the vapors in the ICP discharge. Compromise experimental conditions are reported and calibration functions compared. Limits of detection in 5-μl samples were 8 pg Al and 2.5 ng Si, and after preconcentration of Al with a poly(acrylamidoxime) resin, the detection limit was 1 pg Al. Recovery of 5 μg $\text{Si}\text{ml}$ and 10 ng $\text{Al}\text{ml}$ from aqueous and synthetic standards was 80–85% and 96–103%, respectively.     

Plasma behavior during electrothermal vaporization sample introduction in inductively coupled plasma atomic emission spectrometry

Electrothermal vaporization (ETV) sample introduction in inductively coupled plasma atomic emission spectrometry suffers from severe matrix effects. In the present study, the differences between wet and dry plasma conditions are studied. In addition, the influence of the sample composition was investigated. An inductively coupled plasma optical emission spectrometer, with detection based on charge transfer, allowed the simultaneous measurement of ionic and atomic emission line intensities during the transient signal. Mg and Cr were the test elements. The ion-to-atom line ratio increases at higher power settings, but the changes were larger when a nebulizer was used for sample introduction than with ETV sample introduction. The decrease of ion-to-atom line ratios at increasing observation height was more pronounced when ETV was used, due to the absence of water vapor. The gas flow rate showed a stronger influence for nebulization than for ETV. In the presence of a calcium matrix, lower ion-to-atom line ratios were observed, but the ratio did not change significantly within the transient emission signal. Similar line ratios were observed for different amounts of calcium matrix. The values of ion-to-atom line ratios for Mg and Cr indicate that the plasma ionization and thermal characteristics are not modified due to the presence of the calcium matrix.     

Determination of trace impurities in boron nitride by graphite furnace atomic absorption spectrometry and electrothermal vaporization inductively coupled plasma optical emission spectrometry using solid sampling

Two digestion-free methods for trace analysis of boron nitride based on graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma spectrometry optical emission (ETV-ICP-OES) using direct solid sampling have been developed and applied to the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Si, Ti and Zr in four boron nitride materials in concentration intervals of 1–23, 54–735, 0.05–21, 0.005–1.3, 1.6–112, 4.5–20, 0.03–1.8, 6–46, 38–170 and 0.4–2.3 μg g^− 1, respectively. At optimized experimental conditions, with both methods, effective in-situ analyte/matrix separation was achieved and calibration could be performed using calibration curves measured with aqueous standard solutions. In solid sampling GFAAS, before sampling, the platform was covered with graphite powder and, for determination of Si, also the Pd/Mg(NO₃)₂ modifier was used. In the determination of all analyte elements by solid sampling ETV-ICP-OES, Freon R12 was added to argon carrier gas. For solid sampling GFAAS and ETV-ICP-OES, the achievable limits of detection were within 5 (Cu)–130 (Si) ng g^− 1 and 8 (Cu)–200 (Si) ng g^− 1, respectively. The results obtained by these two methods for four boron nitride materials of different purity grades are compared each with the other and with those obtained in analysis of digests by ICP-OES. The performance of the two solid sampling methods is compared and discussed.     

Determination of the total carbon in soft drinks by tungsten coil electrothermal vaporization inductively coupled plasma spectrometry

A method is developed for the direct determination of carbon in soft drinks by electrothermal vaporization inductively coupled plasma atomic emission spectrometry. A tungsten coil is used as the electrothermal vaporizer, and is extracted from a commercially produced 150 W, 15 V microscope bulb. The standard additions method is employed to correct any matrix effects from the samples. Carbon emission is monitored at 193.091 nm. Carbon content determined for the samples was in the range of 13 to 60 g in one 8 fl oz serving, and these values agreed with the label values in the range 93 to 137% (except for one sample, Orange Fanta, which provided a 200% recovery. This was likely due to non-carbohydrate carbon-containing species in that sample). The precision of the technique was always better than 20% relative standard deviation (n = 10). The detection limits for carbon range from 0.4 to 3 mg L^{− 1}, and absolute detection limits range from 12 ng to 90 ng for a 30 μL aliquot of sample on the coil. This method could be an alternative approach for determining the carbon content of nonvolatile compounds, and complement HPLC–ICP-AES determination of those same species.     

Direct determination of cadmium in urine by tungsten-coil inductively coupled plasma atomic emission spectrometry using palladium as a permanent modifier

Cadmium is determined in urine samples collected from patients with age-related diseases. The urine is simply diluted 1:1 with water and placed on a tungsten coil electrothermal vaporizer treated with 200 μg of a permanent Pd modifier. A straightforward vaporization program is used to deliver the Cd vapor to an inductively coupled plasma atomic emission spectrometer. A high resolution spectrometer and a charge coupled device detector provide spectra across a 4.8 nm window encompassing two separate Cd emission lines: 226.5 and 228.8 nm. The limit of detection is 0.2 μg/L at each wavelength, and the linear dynamic range spans three orders of magnitude. The accuracy as measured with a urine standard reference material is 94%. The Pd modifier continues to be effective even after 150 vaporization cycles. Direct analysis of urine with the Pd modifier using simple aqueous calibration solutions provides results that are comparable to those observed after a much more complex method: chelation, extraction, and internal standardization without the modifier. The mean concentrations found by the two techniques differ by only 9%. The permanent Pd modifier allows direct analysis of limited sample volumes with decreased risks of contamination.     

电热蒸发进样电感耦合等离子体原子发射光谱（ETV－ICP－AES）联用技术研究

本文采用国产部件组装了一套ＥＴＶ－ＩＣＰ－ＡＥＳ仪器体系，对装置的连接及操作参数进行优化。深入系统地考察了分析物的蒸发过程和传输过程，提出了难熔元素的蒸发和传输机理。研究了ＥＴＶ－ＩＣＰ－ＡＥＳ中基体效应，提出了以聚四氟乙烯为氟化剂，氟化辅助ＥＴＶ－ＩＣＰ－ＡＥＳ测定难熔元素的新方法，应用于环境和生物标样中痕量元素分析，获得满意结果。     

Direct determination of major elements in solid plant materials by electrothermal vaporization inductively coupled plasma atomic emission spectrometry

The present work demonstrates the capability of electrothermal vaporization (ETV) to become an important tool of solid sample introduction in ICP-AES for plant sample analysis. Direct determination of Al, Ca, Fe, K, Mg, Mn, Na and Zn was investigated in powdered plant samples. Obtaining good results for major elements in plant samples was governed by some special operating conditions. The sensitivity of the method necessitated the use of ICP in radial view configuration. The behavior of elements during vaporization was studied between 500 and 2600 °C. External calibration was carried out using solid external (cellulose) spiked with aqueous standard solutions. However, performances of the analytical method were found dependent of argon flow rates. Analytical accuracy of the method was tested in three reference materials. Analytical results agreed with certified values when cellulose was used in calibration. However, K could not be determined because of excessive sensitivity. Without cellulose, it was found that Fe results were underestimated and Zn results overestimated. Relative standard deviations varied from 3 to 23%. Limits of detection varied from 1 to 80 ng g⁻¹ from one element to the other for a typical mass sample of 2 mg.     

Possibilities of inductively coupled plasma atomic emission spectrometry with electrothermal vaporization in the analysis of high-purity reagents

Possibilities of electrothermal sample vaporization in inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) in the analysis of high-purity reagents were studied on an example high-purity waters, acid solutions, and trace impurity concentrates. The analytical and background signals in the injection of solutions into inductively coupled plasma (ICP) by pneumatic nebulization and electrothermal vaporization were compared and the of limits of detection in the analysis of high-purity reagents with impurity preconcentration by evaporation were estimated and compared.     

Development of transient data acquisition system for hyphenated techniques coupled with inductively coupled plasma atomic emission spectrometry

A transient data acquisition system for flow injection analysis (FIA), high performance liquid chromatography (HPLC), and electrothermal vaporization (ETV) combined with ICP-AES multi-element instrumentation was developed and successfully applied to the analysis of different types of samples, including human serum, human hair and tea, for simultaneous multi-element determinations. The accuracy of the method was verified with hair reference material. Good agreement between the experimental results and certified values, and also satisfactory recoveries from standard additions, were achleved.     

Design of a compact, aluminum, tungsten-coil electrothermal vaporization device for inductively coupled plasma-optical emission spectrometry

A new compact, aluminum electrothermal vaporization cell was constructed for inductively coupled plasma-optical emission spectrometry analysis. This cell is compact enough to fit within the space occupied by the spray chamber and fits directly to the quartz torch without extraneous tubing through the use of a simple Compression fitting. Sample volumes as low as 10 μL were analyzed with an automated control program for efficient vaporization. Twelve elements were analyzed utilizing a time resolved acquisition method so that real-time data could be generated over a period of 10 s with an average improvement factor of 14 for elements over a wavelength range of 193–445 nm.     

Determination of cadmium,mercury and lead in seawater by electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry

Electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (ETV-ID-ICP-MS) has been applied to the determination of Cd, Hg and Pb in seawater samples. The isotope ratios of the elements studied in each analytical run were calculated from the peak areas of each isotope. Various modifiers were tested for the best signal of these elements. After preliminary studies, 0.15% m/v TAC and 4% v/v HCl were added to the sample solution to work as the modifier. The ETV-ID-ICP-MS method has been applied to the determination of Cd, Hg and Pb in NASS-4 and CASS-3 reference seawater samples and seawater samples collected from Kaohsiung area. The results for reference sample NASS-4 and CASS-3 agreed satisfactorily with the reference values. Results for other samples determined by isotope dilution and method of standard additions agreed satisfactorily. Detection limits were approximately 0.002, 0.005 and 0.001 ng ml⁻¹ for Cd, Hg and Pb in seawater, respectively, with the ETV-ICP-MS method. Precision between sample replicates was better than 20% for most of the determinations.     

Determination of rare earth elements in urine by electrothermal vaporization inductively coupled plasma mass spectrometry

A method was developed for the determination of rare earth elements (REEs) in urine with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICPMS). The undiluted sample was directly injected into the graphite tube and trifluoromethane (Freon-23) was used as chemical modifier in order to reduce the vaporization temperature and the memory effect of most of the lanthanides. The detection limits were in the range 1-10 ng/L with relative standard deviation of 3-5% at concentration levels of 1microg/L, and less than 10-15% at 100 ng/L. Two different procedures, external calibration and a standard additions method, were evaluated to measure the concentration levels of lanthanides in the urine samples and the second procedure was considered to be the best choice for calibration in this work. The level of REEs in urine of 50 healthy volunteers was in the range 5-20 ng/L, above the detection limit of ETV-ICPMS.     

Direct solid sampling electrothermal vaporization of alumina for analysis by inductively coupled plasma optical emission spectrometry

A procedure based on electrothermal evaporation (ETV) and inductively coupled plasma atomic emission spectrometry (ICP-OES) for the determination of trace impurities in Al₂O₃ powders without any sample pretreatment is presented. With the aid of matrix modifier the transport and the evaporation efficiency for refractory compounds could be increased by forming halides with a lower boiling point. As calibration is still a problem in direct solid sample analysis, different calibration approaches including the use of certified reference materials from NIST and standard addition of aqueous solutions of analytes were discussed. The accuracy obtained with calibration and with the standard addition method was shown up for the elements Ca, Fe, Ga, Mg, Mn, Na, Ni and V for the case of Al₂O₃ NIST standard reference material (SRM 699). The ETV–ICP-OES method was used for the analysis of Al₂O₃ powders with impurities in the low μg/g range and the results for the elements Ca, Fe, Ga, Mg, Mn, Na, Ni and V obtained with evaporation of discrete powder amounts with ETV–ICP-OES and slurry evaporation under the use of ultrasonic homogenization during the sampling and ETV–ICP-MS were shown to be in a good agreement.     

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.     

Determination of phosphorus in fertilizers by inductively coupled plasma atomic emission spectrometry

An inductively coupled plasma atomic emission spectrometry (ICP-AES) method was developed for the determination of phosphorus in fertilizers. Total phosphorus, direct extraction available phosphorus (EDTA), and water-soluble phosphorus, reported as phosphorus pentoxide (P205), in 15 Magruder check fertilizers were measured by ICP-AES, and the results were compared with those obtained by the AOAC official method. Five analytical wavelengths of phosphorus, 177.499, 178.287, 213.618, 214.914, and 253.565 nm, were tested for the determination of phosphorus in fertilizers, and their detection limits were obtained. Acid effects of perchloric acid and possible matrix effects of aluminum, calcium, magnesium, potassium, and sodium were negligible for phosphorus determination. Wavelength 213.618 nm was the best analytical wavelength for phosphorus determination by all 3 sample preparation methods for the selected Magruder fertilizers. The results demonstrated that the accuracy and precision of the ICP-AES method were comparable with those of the official methods.     

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. Received: 21 September 1998 / Revised: 30 October 1998 / Accepted: 3 November 1998     

In-situ vaporization and matrix removal for the determination of rare earth impurities in zirconium dioxide by electrothermal vaporization inductively coupled plasma atomic emission spectrometry

A novel method for the determination of trace rare earth impurities in ZrO₂ powder has been developed based on electrothermal vaporization inductively coupled plasma atomic emission spectrometry. A polytetrafluoroethylene slurry was used as a fluorinating reagent to convert both the matrix (Zr) and the analytes (rare earth elements) into fluorides with different volatilities at a high temperature in a graphite furnace. The more volatile ZrF₄ was removed in-situ by selective vaporization prior to the determination of the analytes, removing matrix spectral interferences. Under optimum operating conditions, the absolute detection limits of the analytes varied from 0.04 ng (Yb) to 0.50 ng (Pr) with relative standard deviations less than 5%. The recommended approach has been successfully applied to the determination of trace rare earth impurities (La, Pr, Eu, Gd, Ho and Yb) in ZrO₂ powder and the results were in good agreement with those obtained by pneumatic nebulization inductively coupled plasma atomic emission spectrometry after the separation of the matrix using a solvent extraction procedure.     

Chelation of urinary cadmium with ammonium pyrrolidine dithio-carbamate prior to determination by tungsten-coil inductively coupled plasma atomic emission spectrometry

Cadmium in the urine samples of patients with age-related disease forms a complex with a chelating agent, ammonium pyrrolidine dithio-carbamate, and the complex is extracted with methyl isobutyl ketone. One milliliter of urine provides three separate 200-μl aliquots of extract, so a preconcentration factor of 5/3 is observed. In this manner, the Cd is effectively separated from the complex urine matrix. An internal standard, Bi, is added to improve both precision and accuracy. The extracts are analyzed by inductively coupled plasma atomic emission spectrometry using a tungsten-coil as an electrothermal vaporizer. A 20-μl aliquot of the extract is injected directly onto the coil. Two Cd atomic emission lines are observed simultaneously: 228.8 nm and 226.5 nm. The limits of detection at these wavelengths are 0.04 and 0.2 μg/l, respectively. Without the extraction technique, the detection limit is 0.4 μg/l at the 228.8-nm line. With the internal standard technique, the accuracy as measured with a urine standard reference material is 98%. Six urine samples collected from patients with age-related diseases are found to contain Cd levels in the range 0.9 to 4.1 μg/l. The precision associated with the measurement of these real samples is 6.2% relative standard deviation. The technique provides off-wavelength background correction and simultaneous determination at two different wavelengths, so samples that are limited in volume can still be analyzed with a high degree of confidence.