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.     

A new approach of direct sample-digestion before vaporization for determination of a metal in rocks by inductively coupled plasma atomic emission spectrometry.

A new approach to sample digestion, subsequent vaporization and introduction to an inductively coupled plasma (ICP) atomic emission spectrometer was developed for the direct determination of magnesium. To each small sample cuvette made of tungsten, a ground rock sample was precisely weighed. The cuvette was situated on a tungsten boat furnace. Ammonium fluoride solution was added to the cuvette as a chemical modifier. After the on-furnace digestion has been completed, the analyte, magnesium, in the cuvette was vaporized and introduced into the ICP atomic emission spectrometer. Since the powdered samples were wet-digested in the sample cuvettes prior to vaporization, they could be analyzed by using a calibration curve prepared from aqueous standard solutions. This method was applied to the determination of magnesium in several standard reference materials with satisfactory results.     

Determination of Trace Chlorine in Fine Ceramics by ICP-AES Using Tungsten Boat Furnace Vaporizer and Exchangeable Sample Cuvette System as a Direct Solid Sampler

A new approach to simple solid sample digestion, subsequent vaporization, and introduction into an inductively coupled plasma was developed for the direct determination of chlorine in fine ceramic materials by atomic emission spectrometry. To each small sample cuvette made of tungsten, a powder sample was placed and weighed accurately. Following an addition of modifier solution, the cuvette was positioned on the tungsten boat furnace incorporated an electrothermal vaporizer. Then, the analyte in the sample cuvette was vaporized and introduced into the plasma; the major components of ceramic being retained. The solid ceramic samples were analyzed by using an external calibration curve prepared with the aqueous standard solutions. The detection limit of chlorine was estimated to be 0.71 ng, which corresponds to 59 ng g^?1 of the chlorine concentration in solid ceramic materials. The relative standard deviation was calculated to be 3.2%. The analytical results in various ceramic materials are described.     

Direct determination of lead in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after furnace-fusion in the sample cuvette-tungsten boat furnace

The newly conceived electrothermal vaporization (ETV) system using a tungsten boat furnace (TBF) sample cuvette was designed for the direct analysis of solid samples with detection by inductively coupled plasma mass spectrometry (ICP-MS). Into this small sample cuvette, a solid mixture of the biological samples and diammonium hydrogenphosphate powder as a fusion flux was placed and situated on a TBF. Tetramethylammonium hydroxide solution was added to the mixture. After the on-furnace digestion had been completed, the analyte in the cuvette was vaporized and introduced into the ICP mass spectrometer. The solid samples were analyzed by using a calibration curve prepared from the aqueous standard solutions. The detection limit was estimated to be 5.1 pg of lead, which corresponds to 10.2 ng g^–1 of lead in solid samples when a prepared sample amount of 1.0 mg was applied. The relative standard deviation for 8 replicate measurements obtained with 100 pg of lead was calculated to be 6.5%. The analytical results for various biological samples are described.     

Direct determination of lead in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after furnace-fusion in the sample cuvette-tungsten boat furnace

The newly conceived electrothermal vaporization (ETV) system using a tungsten boat furnace (TBF) sample cuvette was designed for the direct analysis of solid samples with detection by inductively coupled plasma mass spectrometry (ICP-MS). Into this small sample cuvette, a solid mixture of the biological samples and diammonium hydrogenphosphate powder as a fusion flux was placed and situated on a TBF. Tetramethylammonium hydroxide solution was added to the mixture. After the on-furnace digestion had been completed, the analyte in the cuvette was vaporized and introduced into the ICP mass spectrometer. The solid samples were analyzed by using a calibration curve prepared from the aqueous standard solutions. The detection limit was estimated to be 5.1 pg of lead, which corresponds to 10.2 ng g(-1) of lead in solid samples when a prepared sample amount of 1.0 mg was applied. The relative standard deviation for 8 replicate measurements obtained with 100 pg of lead was calculated to be 6.5%. The analytical results for various biological samples are described.     

Simple and convenient analytical method for the direct determination of chlorine species by ETV-ICP-AES using tungsten boat furnace vaporiser and exchangeable small sample cuvettes

A tungsten boat furnace vaporiser and an exchangeable sample cuvette system were applied for the direct determination of chlorine in plastic samples by electrothermal vaporisation inductively coupled plasma atomic emission spectrometry. Each piece of plastic samples was moulded into a thin film, and weighed into small sample cuvettes. An ethanolic solution of the modifier potassium hydroxide and an organic solvent were added to each sample cuvette. The contents including the plastic piece were spread over the bottom of each sample cuvette by warming on a hotplate. After the preparation, one of the cuvettes was placed in the tungsten boat furnace equipped with the electrothermal vaporiser. The temperature was gradually elevated. At the flash vaporisation step of 1800 °C, the analyte was vaporised and introduced into the ICP to measure an atomic emission assignable to Cl I 134.724 nm. A widely spread thin layer of the plastic facilitated its rapid evaporation and introduction into an ICP atomic emission spectrometer. Since all the chlorine species were on-furnace decomposed to form potassium chloride during the pretreatment, the solid samples were analysed using a calibration curve prepared from the aqueous standard solutions. By using this system, a detection limit of 1.5 μg g⁻¹ of chlorine in solid plastic samples was established when a sample amount taken of 2 mg was studied. The exchangeable sample cuvette technique makes it possible to measure a number of sample sequentially by preparing a lot of sample cuvettes prior to analysis. Approximately 20 batches could be vaporised per hour. Analytical results of some plastic samples that were analysed by this technique are given in this report.     

Direct determination of bromine in plastics by electrothermal vaporization/inductively coupled plasma mass spectrometry using a tungsten boat furnace vaporizer and an exchangeable sample cuvette system

A tungsten boat furnace vaporization inductively coupled plasma mass spectrometry (TBF/ICP‐MS) method has been applied to the direct determination of bromine in plastic samples. In the pretreatment, the plastic sample is spread over a small sample cuvette made of tungsten by treating it with a strongly basic organic solution, e.g., octanol or diisobutyl ketone in the presence of potassium hydroxide. The cuvette is placed on a tungsten boat furnace, with which the electrothermal vaporizer is equipped. At the vaporization step, a widely spread thin layer of the sample facilitates its efficient evaporation and introduction into an ICP mass spectrometer. The most remarkable feature is that all the bromine species in plastic samples are decomposed to form a thermally stable inorganic salt during the pretreatment procedure. Therefore, the bromine content in plastic samples can be measured by a calibration curve method constructed with an aqueous standard solution of potassium bromate(V). The detection limit (3σ) was estimated to be 0.77 pg of bromine, which corresponds to a concentration of 0.31 ng g^?1 of bromine in plastic samples when a sample amount taken of 2.5 mg is studied. The relative standard deviation was calculated to be 2.2%. Analytical results of some plastic samples, which contained both inorganic bromide salts and also organic bromine species, are given. Copyright © 2010 John Wiley & Sons, Ltd.     

Direct determination of cadmium in solids using a capacitively coupled microwave plasma atomic emission spectrometer

A capacitively coupled microwave plasma (CMP) operating at 800 W was examined for the direct determination of cadmium in solids. The laboratory-constructed system contained a tungsten cup electrode capable of holding microsample quantities. A low-powered plasma was used to heat the sample, while at higher powers the plasma was used for sample vaporization and excitation. This plasma enabled thermal vaporization (TV) sample introduction to be accomplished in situ as the plasma formed directly around the sample. Thus, the need for sample preparation, procedural steps and sample transport was eliminated. This technique was capable of the direct determination of trace elements in solid samples in less than 5 min. The effects of experimental parameters such as gas flow rate, atomization power and electrode position were investigated. Detection limits obtained for Cd by TV-CMP-AES were in the picogram range with a relative standard deviation of <20%. The accuracy and precision of the method were also evaluated by measuring Cd in several NIST Standard Reference Materials.     

Optimization of ETV-ICP-MS conditions for the determination of multi-elements in semiconductor grade acids

The performance of an electro thermal vaporization (ETV) unit as a sample introduction device for an inductively coupled plasma mass spectrometer (quadrupole-ICP-MS) was evaluated. The technique was found to have several advantages over the conventional nebulization method. Some features of ETV-ICP-MS for single element determination have been investigated. Attempts were made to optimize the experimental parameters such as vaporization temperature, vaporization interval and carrier gas flow rate. The study highlights on the determination of Cr, Mn, Al and Na. A compromise condition for multi-element determination was suggested and tested from single-element optimum conditions obtained. 25 L solution was used for the analysis. Results obtained for the analysis of conc. HCl samples are also reported.     

On-line microwave oven digestion flame atomic absorption analysis of solid samples

A manifold has been developed for on-line microwave oven digestion and flame atomic absorption spectrometric (FAAS) determination of metallic elements in solid samples. The use of a closed flow system permits sample treatment before analysis by FAAS, the direct injection of slurries avoids a filtration step and the interconnection of two conventional rotary injection valves allows the rapid introduction of samples and standards. The determination of lead in sewage sludge was employed as a test system for the proposed on-line sample digestion manifold. The procedure has a limit of detection of 0.2 μg Pb g^?1.     

Investigations of reactions involved in electrothermal atomic absorption procedures: Part 9. An atomization system with controlled atmosphere and temperature for the determination of volatile elements in complex matrices

A controlled temperature controlled atmosphere atomization system is described. The sample is placed on a tungsten wire provided with temperature-controlled heating. After thermal pretreatment of the sample the wire is inserted into a hot quartz tube and rapid vaporization is accomplished by separate electrothermal heating. The pyrolysis products formed are mixed with a gas buffer and are passed through two equilibrium zones. The residence time of the analyte in the system is of the order of seconds so that the probability of attaining a state close to equilibrium is high for high temperatures. A third zone is placed perpendicularly to the others and constitutes the atomic absorption measuring cell. The usefulness of the system is illustrated for the determination of lead, bismuth, cadmium and zinc. The system provides unique possibilities in controlling interference effects in complex matrices. Examples are given for lead in concentrated chloride and sulphate solutions. Good agreement between the experimental results and high-temperature equilibrium calculations was obtained for a large variation in the composition of the gas phase.     

Sensitive determination of bromine and iodine in aqueous and biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry using tetramethylammonium hydroxide as a chemical modifier

A procedure for the simultaneous determination of bromine and iodine by inductively coupled plasma (ICP) mass spectrometry was investigated. In order to prevent the decrease in the ionization efficiencies of bromine and iodine atoms caused by the introduction of water mist, electrothermal vaporization was used for sample introduction into the ICP mass spectrometer. To prevent loss of analytes during the drying process, a small amount of tetramethylammonium hydroxide solution was placed as a chemical modifier into the tungsten boat furnace. After evaporation of the solvent, the analytes instantly vaporized and were then introduced into the ICP ion source to detect the (79)Br(+), (81)Br(+), and (127)I(+) ions. By using this system, detection limits of 0.77 pg and 0.086 pg were achieved for bromine and iodine, respectively. These values correspond to 8.1 pg mL(-1) and 0.91 pg mL(-1) of the aqueous bromide and iodide ion concentrations, respectively, for a sampling volume of 95 microL. The relative standard deviations for eight replicate measurements were 2.2% and 2.8% for 20 pg of bromine and 2 pg of iodine, respectively. Approximately 25 batches were vaporizable per hour. The method was successfully applied to the analysis of various certified reference materials and practical situations as biological and aqueous samples. There is further potential for the simultaneous determination of fluorine and chlorine.     

Application of an ETV-ICP system for the determination of elements in human hair

When determining element contents in hair samples without sample digestion it is necessary to analyze large sample volumes in order to minimize problems of inhomogeneity of biological sample materials. Therefore an electrothermal vaporization system (ETV) is used for solid sample introduction into an inductively coupled plasma (ICP) for the determination of matrix and trace elements in hair. This paper concentrates on the instrumental aspects without time consuming sample preparation. The results obtained for optimization tests, ETV operating parameters and ICP operating parameters, are shown and discussed. Standard additions are used for calibration for the determination of Zn, Mg, and Mn in human hair. Studies including reproducibility and detection limits for chosen elements have been carried out on certified reference materials (CRMs). The determination of reproducibility (relative standard deviation (RSD) of n = 10) and detection limits (DLs) of Zn (RSD < 8.5%, DL < 0.8 μ g⁻¹), Mn (RSD < 14.1%, DL < 0.3 μ g⁻¹), and Mg (RSD < 7.4%, DL < 6.6 μ g⁻¹) are satisfactory. The concentration values found show good agreement with the corresponding certified values. Further sample preparation steps, including hair sampling, washing procedure and homogenization for hair, relating to measurements of real hair samples are described.     

Determination of Lead in Lipstick by Direct Solid Sampling High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry: Comparison of Two Digestion Methods

A new analytical procedure for the determination of lead in lipstick has been developed using direct solid sampling high resolution continuum source graphite furnace atomic absorption spectrometry (SS HR CS GFAAS). The performance of this method has been compared to acid digestion methods for sample preparation, with or without hydrofluoric acid (HF) with inductively coupled plasma mass spectrometry (ICP-MS) detection. Good reliability was obtained for all three methods; the results obtained for certified reference materials with concentrations between 1 and 20 ppm were in agreement with the certified values. However, for materials with complex matrices, such as pearl or Ca-Na borosilicate, only ICP-MS with HF sample digestion or AAS with direct solid sampling allowed complete recovery of lead. To avoid the use of hazardous acids, the development of SS HR CS GFAAS is an interesting alternative. With the AAS method, a characteristic mass of 13.2 pg of lead was obtained, and the limit of detection was 0.005 µg/g. The performance of the method was evaluated by determining lead in lipstick. The use of the solid sampling technique constitutes a good alternative for accurate and rapid determination of lead content in lipstick and cosmetic raw materials, with a suitable limit of detection and a reduced risk of contamination or of analyte loss. Another alternative would be to use ICP-MS determination in conjunction with microwave-assisted acid digestion without the use of HF, which implies accepting a quantification of “nearly total” lead, closer to a “bio-extractible” fraction.     

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.     

ETV-ICP-AES联用技术的蒸发器研究

ETV-ICP-AES是样品电热气化/电感耦合等离子体激发的联用技术^[1～7],具有进样效率高并可进行微升级样品分析的特点.ETV-ICP-AES多采用石墨炉或石墨棒蒸发器.因此,蒸发器的结构、形状、升温速率以及温度分布等对分析信号有很大的影响^[3,4].本文研究了蒸发器的接口、形状、结构的影响;自行设计了插入式平台,减小死体积,还研究了在载气单向连续流动的情况下,石墨炉内部温度的大致分布,讨论了平台蒸发和管壁蒸发.     

Direct Determination of Lead in Whole Blood Using Electrothermal Vaporization Inductively Coupled Plasma Atomic Emission Spectrometry

Abstract

A carbon rod atomizer was used for sample introduction into a commercial inductively coupled plasma for the determination of lead in whole blood. Samples of known lead concentration were either treated with Triton-X or nitric acid or diluted 1+5 with distilled water and analyzed by comparison against graphs obtained using aqueous solutions and using the standard additions method. Both approaches produced similar results indicating no appreciable matrix influence. The Pb concentration values obtained were in close agreement with those previously determined by ETA-AAS, Delves′ cup-FAAS and anodic stripping voltammetry. Signal integration and careful selection of the measurement period were critical to obtain accurate results. Derived concentrations were shown to be essentially independent of the heating rate of the vaporization unit and the length of tubing used to transport the material into the plasma. Using a 1 μg ml^?1 lead aqueous standard, a signal to background ratio of 5.5 was obtained under optimized conditions. Relative standard deviations of the blank and the analytical signal were 0.2 and 1.8%., respectively. An aqueous solution detection limit of 0.007 μg ml^?1 was calculated for lead.     

Applications of laser ablation and electrothermal vaporization as sample introduction techniques for ICP-MS

The field of applications of ICP-MS can be further increased by the use of special sample introduction techniques such as laser ablation (LA) and electrothermal vaporization (ETV). In both cases a tandem source for mass spectrometry is formed by the sample introduction device and the ICP. The first source is specifically designed for the volatilization of a sample and it can be used to introduce selectively only certain parts of a sample into the ICP-MS, based either on local distribution (LA) or volatility (ETV). Applications of LA-ICP-MS are the determination of distribution patterns of minor constituents in solid samples such as ceramics, alloys or hard biological structures. Homogeneity testing in the first two types of samples or determination of distribution patterns of trace elements in the latter can be carried out rapidly with high spatial resolution on a multielement basis. The possibility of on-line separation between fractions of different volatility in a sample with ETV-ICP-MS is demonstrated for volcanic eruption products and other samples.     

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     

Slurry sample introduction with fluorinating electrothermal vaporization for the direct ICP-AES determination of boron in plant leaves

Summary The slurry sample introduction with fluorinating electrothermal vaporization has been applied to ICP-AES for the determination of boron in plant leaves. The main working parameters for ETV-ICP-AES, such as r.f. power, gas flow rate, drying temperature and atomization temperature have been studied. The concentration of the fluorinating agent polytetrafluoro-ethylene was examined for the boron determination. The matrix concentrations of Na, K, Ca and Mg up to 5 mg/ml do not interfere with the fluorinating vaporization of boron. Several plant samples were analysed with the standard addition method. A good agreement of analytical results between this method and a spectrophotometric method was obtained. The determined value of boron in NBS SRM 1573 tomato leaves coincides with literature values.