Electrothermal vaporization in inductively coupled plasma atomic emission spectrometry for direct multielement analysis of food samples with slurry sampling

Slurry sampling followed by electrothermal vaporization (ETV) was used as sample introduction technique in inductively coupled plasma atomic emission spectrometry (ICP-AES) for the direct determination of trace elements in food samples. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote vaporization and the transportation of analytes. The main factors affecting the analytical signals were investigated in detail. Under optimum operating conditions, the detection limits (DL) for this method varied from 1.8 (Cu) to 215 ng/mL (Zn), while the relative standard deviations (RSD) were in the range 2.6% (Cu)-7.2% (Zn). The proposed method was successfully applied to the direct determination of trace amounts of V, Cu, Cr, Fe, Zn, and La in rice without any chemical pretreatment. The precision was evaluated by analyzing a standard reference material (tea leaves, GBW 07605) and comparing the results from this method with results obtained by pneumatic nebulization (PN) ICP-AES after the wet-chemical decomposition of the same sample.From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 3, 2005, pp. 286–290.Original English Text Copyright © 2005 by Chen.This article was submitted by the author in English.     

Electrothermal vaporization system using furnace-fusion technique for the determination of lead in botanical samples by inductively coupled plasma atomic emission spectrometry

A new approach to sample digestion, subsequent vaporization and introduction into an inductively coupled plasma atomic emission spectrometer was developed for the direct determination of lead. To each small sample cuvette made of tungsten, a mixture of a ground solid sample and powdered diammonium hydrogenphosphate was precisely weighed. The cuvette was positioned onto the tungsten boat furnace (TBF) incorporating a vaporizer. Tetramethylammonium hydroxide solution was added. Then the cuvette was heated and maintained at a wet-digestion temperature to decompose the solid sample. After digestion, the temperature was elevated to generate the analyte vapor for introduction into a plasma. Since the solid samples were wet-digested in the sample cuvettes before vaporization, they could be analyzed by using a calibration curve prepared from aqueous standard solutions. This method was applied to the determination of lead in several biological materials with satisfactory results.     

Electrothermal vaporization system using furnace-fusion technique for the determination of lead in botanical samples by inductively coupled plasma atomic emission spectrometry

A new approach to sample digestion, subsequent vaporization and introduction into an inductively coupled plasma atomic emission spectrometer was developed for the direct determination of lead. To each small sample cuvette made of tungsten, a mixture of a ground solid sample and powdered diammonium hydrogenphosphate was precisely weighed. The cuvette was positioned onto the tungsten boat furnace (TBF) incorporating a vaporizer. Tetramethylammonium hydroxide solution was added. Then the cuvette was heated and maintained at a wet-digestion temperature to decompose the solid sample. After digestion, the temperature was elevated to generate the analyte vapor for introduction into a plasma. Since the solid samples were wet-digested in the sample cuvettes before vaporization, they could be analyzed by using a calibration curve prepared from aqueous standard solutions. This method was applied to the determination of lead in several biological materials with satisfactory results.     

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.     

Analytical evaluation of electrothermal vaporization/low-pressure inductively coupled plasma atomic emission spectrometry for trace elemental analysis in microliter samples

A novel method for the determination of trace elements in microliter samples using the tantalum filament electrothermal vaporization/low-pressure inductively coupled plasma (ETV/LP-ICP) atomic emission spectrometry has been developed. An improved tantalum filament ETV was directly coupled with LP-ICP system for efficient vaporization of microliter samples and further quantitative analysis. The experimental parameters including ETV current, rf power and mass flow rate of argon carrier gas were optimized using the copper emission signal produced by 5 μl of standard solution (5 μg/ml). Under the optimized condition, the analytical performances including linearity, precision and detection limit for the developed system were investigated. Absolute detection limits in the range of 22–391 pg for selected eight elements (Fe, Cu, Cr, Mn, Pb, K, Zn and Mg) were obtained with satisfactory precision (<8.9% RSD). The feasibility of the developed system has been demonstrated by analyzing wheat gluten NIST standard sample.     

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.     

Study on the direct analysis of solid powder biological samples using fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry with PTFE slurry modifier

A method has been described for the direct determination of Ti, Cu, Mn, Cr and Cd in solid biological samples without any chemical pretreatment by fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) with slurry sampling. A polytetrafluorethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of the analytes from the graphite furnace. The interface between furnace device and ICP torch and the main factors affecting the analytical signal were investigated systematically. The detection limits for the determination of Ti, Cu, Mn, Cr and Cd are 6.3, 4.7, 10, 13 and 278 ng/mL, respectively; the relative standard deviations are in the range of 1.5 (Mn) ∼4.0% (Cd) after optimization of the operating conditions. The recommended approach has been applied to directly determine the trace elements of interest in the Chinese traditional medicine Loulu and in the solid biological standard reference material (peach leaves, GBW 08501) with satisfactory results. Received: 28 December 1998 / Revised: 9 February 1999 / Accepted: 12 February 1999     

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.     

Study on the direct analysis of solid powder biological samples using fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry with PTFE slurry modifier

A method has been described for the direct determination of Ti, Cu, Mn, Cr and Cd in solid biological samples without any chemical pretreatment by fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) with slurry sampling. A polytetrafluorethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of the analytes from the graphite furnace. The interface between furnace device and ICP torch and the main factors affecting the analytical signal were investigated systematically. The detection limits for the determination of Ti, Cu, Mn, Cr and Cd are 6.3, 4.7, 10, 13 and 278 ng/mL, respectively; the relative standard deviations are in the range of 1.5 (Mn) ∼4.0% (Cd) after optimization of the operating conditions. The recommended approach has been applied to directly determine the trace elements of interest in the Chinese traditional medicine Loulu and in the solid biological standard reference material (peach leaves, GBW 08501) with satisfactory results. Received: 28 December 1998 / Revised: 9 February 1999 / Accepted: 12 February 1999     

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.     

A helium inductively coupled plasma for atomic emission spectrometry

An annular helium inductively coupled plasma (He ICP) was generated at atmospheric pressure. No external cooling was used to stabilize the plasma. Aqueous solution was injected into the plasma without any difficulty. Preliminary results revealed that the annular He ICP was capable of exciting elements such as Cl and Br which possess high excitation energies. Atomic emission detection limits for Cl and Br were improved by factors of 63 and 34, respectively, as compared to the results obtained from the argon inductively coupled plasma. The excitation temperature of the annular He ICP (4180 K) was less than that of an Ar ICP (5570 K).     

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。     

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.     

Electrothermal vaporization for the determination of halogens by reduced pressure inductively coupled plasma mass spectrometry

Trace level quantities of some halogen elements are determined by coupling tungsten filament electrothermal vaporization (ETV) with reduced pressure argon inductively coupled plasma mass spectrometry (ICP-MS). Microliter aqueous samples of chlorides, bromides and iodides were loaded on the tungsten wire, where they were dried at constant current and then vaporized by using a high-capacity condenser discharge. On decreasing the pressure of the plasma, analyte intensity increased sharply. The reduced pressure ICP is seen to give a much narrower, more intense signal profile. The detection limits for bromine and chlorine improved about 10 times compared with an atmospheric pressure ICP ionization source. An electron collision ionization mechanism may contribute most to halogen ionization for reduced pressure ICP. The linear dynamic range was over three orders of magnitude. The precision was generally between 3–8%. Matrix effect was investigated with Na as a matrix element. Absolute detection limits for the elements studied are in the picogram to subnanogram range.     

Comparison between X-ray fluorescence and inductively coupled plasma atomic emission spectrometry in the analysis of sediment samples

Two multielemental analytical techniques, X-ray fluorescence analysis (XRF) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used for the analysis of the elemental composition of sediment samples from a marsh and standard reference materials. The sediment samples were pretreated with different methods which are widely used in practice. A comparison was made not only between the concentrations obtained by the different methods, but also between the statistical conclusions derived from the processing of the experimental results. Good agreement was found for some elements, e.g. Mn, Zn and Sr, while the concentrations and the statistical conclusions were shown to depend on the analytical method used in the case of other elements, e.g. Fe and Zr.     

Laser vaporization of solid metal samples into an inductively coupled plasma

A laser vaporization-inductively coupled plasma system has been developed and tested for the direct analysis of solid metal samples. In this system the sample (normal emission spectroscopy metal disc standards) is vaporized utilizing a pulsed ruby laser and the vaporized material is swept into the ICP. Multichannel spectral data are simultaneously acquired using a photodiode array spectrometer. System parameters that have been investigated include ICP emission signal duration, number of laser shots to be used for a determination, the time between laser shots, free running or Q-switched laser operation, and the effect of laser focus. Analytical curves are presented for aluminum and brass samples.     

Determination of cadmium by an improved double chamber electrothermal vaporization inductively coupled plasma atomic emission spectrometry

An improved double chamber electrothermal vaporization (ETV) system was designed. A new inner chamber and its bottom plate made of quartz glass were attached with carrier support gas inlet port for the determination of cadmium by inductively coupled plasma atomic emission spectrometry (ICP-AES). The use of the inner chamber in combination with the plate played important roles to transport the metal vapor efficiently into argon ICP. Ten-μl sample aliquots were dried at 100 °C and subsequently heated at 1000 °C on the tungsten boat furnace. The evolved vapor was swept into the ICP source through PTFE tubing and the inner chamber by a 0.8 l/min H₂ (7%)-Ar carrier gas. The performance parameters of ETV-ICP-AES such as temperature program and gas flow rate were evaluated using cadmium standard solution. Under the optimized experimental conditions, the best attainable detection limit at Cd II 214.438 nm line was 0.2 ng/ml with linear dynamic ranges of 50 to 10,000 ng/ml for cadmium. The instrumental precision expressed as the relative standard deviation (RSD) from ten replicate measurements of 10,000 ng/ml for cadmium by ETV-ICP-AES was 0.85%. The present method has been successfully applied to the determination of cadmium in zinc-base materials.