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 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.     

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 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.     

Determination of vanadium and titanium in steel by inductively coupled plasma atomic emission spectrometry with modified use of a tungsten boat furnace atomizer for atomic absorption spectrometry

For electrothermal sample introduction, a commercially available tungsten boat atomizer for atomic absorption spectrometry (AAS) was transferred to a vaporizer for inductively coupled plasma atomic emission spectrometry (ICP-AES). The modification retained as much of the original design of the atomizer as possible, so that the apparatus could be switched easily between conventional tungsten boat furnace (TBF)-AAS and TBF-ICP-AES. By using this system, a procedure for the determination of vanadium and titanium in steel was investigated. The detection limits (S/N=3) of vanadium and titanium were 3.9 and 1.5 ng ml^?1, respectively. The relative standard deviations for five replicate determinations were ca. 3% for both elements. The calibration graphs were linear up to 100 μg ml^?1 vanadium(V) and 10 μg ml^?1 titanium(IV). Results of analyses of some low-alloy steel samples are given.     

Some observations on electrothermal vaporisation for sample introduction into the inductively coupled plasma

The development and analytical utility of electrothermal vaporisation techniques employing a graphite rod for sample introduction into the inductively coupled plasma (ICP) are assessed. In most instances detection limits are superior to those obtained with nebulisation based systems, and are comparable to those obtained with graphite furnace atomic absorption spectrometry. A model is derived for the sample injection process. Additionally the major interference and alteration of the plasma excitation phenomena ensuing from the sample introduction of a solvent free aerosol are discussed in order to assess the analytical potential of the technique for routine μl volume sample introduction in ICP spectrometry. The capability for simultaneous multi-element analyses is maintained with the electrothermal vaporisation technique.     

Analytical evaluation of totally pyrolytic graphite cuvettes for electrothermal atomic absorption spectrometry

The performance characteristics of electrothermal atomiser cuvettes made of totally pyrolytic graphite (TPG) are compared to those of coated and uncoated electrographite. An analytical programme was devised to determine the useful operational lifetime of each cuvette and assess the effect of cuvette age on the sensitivity and precision of the determinations of lead, manganese and vanadium by atomic absorption spectrometry. The main advantages of TPG are enhanced cuvette durability and improved sensitivity and precision, especially for involatile elements. The characteristics of uncoated electrographite were generally unsatisfactory compared to the pyro-coated and TPG cuvettes studied.     

Generation of a methylbismuth species and its electrothermal vaporization for the determination of bismuth by inductively coupled plasma mass spectrometry

Inorganic bismuth(III) was converted to a methylbismuth species, possibly trimethylbismuth, by a thermochemical reaction with methyllithium. It instantly vaporized and was then introduced into the ICP ion source to detect the ²⁰⁹Bi signal. Utilizing an exchangeable small sample cuvette placed on the tungsten boat furnace for the reaction was very favorable from the viewpoints of easy handling, no memory effect, and maintenance of furnace conditions. In this manner, the analyte was vaporized at quite a low temperature (150 °C). The detection limit (3σ) was 0.13 pg of bismuth and the precision in relative standard deviation for 5.0 pg of bismuth was determined to be 3.8% (n = 7). Received: 6 June 1999 / Revised: 31 August 1999 / /Accepted: 23 September 1999     

Generation of a methylbismuth species and its electrothermal vaporization for the determination of bismuth by inductively coupled plasma mass spectrometry

Inorganic bismuth(III) was converted to a methylbismuth species, possibly trimethylbismuth, by a thermochemical reaction with methyllithium. It instantly vaporized and was then introduced into the ICP ion source to detect the 209Bi signal. Utilizing an exchangeable small sample cuvette placed on the tungsten boat furnace for the reaction was very favorable from the viewpoints of easy handling, no memory effect, and maintenance of furnace conditions. In this manner, the analyte was vaporized at quite a low temperature (150 degrees C). The detection limit (3sigma) was 0.13 pg of bismuth and the precision in relative standard deviation for 5.0 pg of bismuth was determined to be 3.8% (n = 7).     

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.     

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.     

Separate vaporisation of boric acid and inorganic boron from tungsten sample cuvette-tungsten boat furnace followed by the detection of boron species by inductively coupled plasma mass spectrometry and atomic emission spectrometry (ICP-MS and ICP-AES)

Utilising extremely different vaporisation properties of boron compounds, the determination procedures of volatile boric acid and total boron using tungsten boat furnace (TBF) ICP-MS and TBF-ICP-AES have been investigated. For the determination of volatile boric acid by TBF-ICP-MS, tetramethylammonium hydroxide (TMAH, Me₄NOH) was used as a chemical modifier to retain it during drying and ashing stages. As for the total boron, not only non-volatile inorganic boron such as boron nitride (BN), boron carbide (B₄C), etc. but also boric acid (B(OH)₃) was decomposed by a furnace-fusion digestion with NaOH to produce sodium salt of boron, a suitable species for the electrothermal vaporisation (ETV) procedure. The proposed method was applied to the analysis of various standard reference materials. The analytical results for various biological and steel samples are described.     

Elemental analysis of silicon based minerals by ultrasonic slurry sampling electrothermal vaporisation ICP-MS

Ultrasonic slurry sampling electrothermal vaporisation inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) was applied to the elemental analysis of silicate based minerals, such as talc or quartz, without any pre-treatment except the grinding of the sample. The electrothermal vaporisation device consists of a tungsten coil connected to a home-made power supply. The voltage program, carrier gas flow rate and sonication time were optimised in order to obtain the best sensitivity for elements determined. The relationship between the amount of sample in the slurry and the signal intensity was also evaluated. Unfortunately, in all cases, quantification had to be carried out by the standard additions method owing to the strong matrix interferences. The global precision of the proposed method was always better than 12%. The limits of detection, calculated as three times the standard deviation of the blank value divided by the slope of the calibration curve, were between 0.5 ng/g for As and 3.5 ng/g for Ba. The method was validated by comparing the concentrations found for Cu, Mn, Cr, V, Li, Pb, Sn, Mg, U, Ba, Sr, Zn, Sb, Rb and Ce using the proposed methodology with those obtained by conventional nebulisation ICP-MS after acid digestion of the samples in a microwave oven. The concentration range in the solid samples was between 0.2 μg/g for Cr and 60 μg/g for Ba. All results were statistically in agreement with those found by conventional nebulisation.     

Tungsten devices in analytical atomic spectrometry

Tungsten devices have been employed in analytical atomic spectrometry for approximately 30 years. Most of these atomizers can be electrically heated up to 3000 °C at very high heating rates, with a simple power supply. Usually, a tungsten device is employed in one of two modes: as an electrothermal atomizer with which the sample vapor is probed directly, or as an electrothermal vaporizer, which produces a sample aerosol that is then carried to a separate atomizer for analysis. Tungsten devices may take various physical shapes: tubes, cups, boats, ribbons, wires, filaments, coils and loops. Most of these orientations have been applied to many analytical techniques, such as atomic absorption spectrometry, atomic emission spectrometry, atomic fluorescence spectrometry, laser excited atomic fluorescence spectrometry, metastable transfer emission spectroscopy, inductively coupled plasma optical emission spectrometry, inductively coupled plasma mass spectrometry and microwave plasma atomic spectrometry. The analytical figures of merit and the practical applications reported for these techniques are reviewed. Atomization mechanisms reported for tungsten atomizers are also briefly summarized. In addition, less common applications of tungsten devices are discussed, including analyte preconcentration by adsorption or electrodeposition and electrothermal separation of analytes prior to analysis. Tungsten atomization devices continue to provide simple, versatile alternatives for analytical atomic spectrometry.     

Determination of erbium and neodymium dopants in bismuth tellurite optical crystals by graphite furnace atomic spectrometry techniques

Application of concentrated HCl as a solvent and triammonium citrate (TAC) as a chemical modifier is advantageous for the determination of Er and Nd dopants in bismuth tellurite (Bi₂TeO₅) single crystals by graphite furnace atomic absorption spectrometry (GFAAS). The use of mini-flow of the internal gas, instead of gas stop, results in better precision at a price of a relatively small decrease in sensitivity. By evaluating integrated absorbance (A_int) signals for the GFAAS measurements (in the presence of matrix and TAC additive), characteristic mass values of 42 and 320 pg, and a limit of detection (LOD) of 4.9 and 131 μg l⁻¹ are found for Er and Nd, respectively. These LOD data correspond to 0.78 μg g⁻¹ Er and 21 μg g⁻¹ Nd in the solid samples. The calibration curves are linear up to 0.33 and 2.9 mg l⁻¹ concentrations in the solutions of Er and Nd, respectively. The ratio of the A_int signals of Er and Nd under gas stop and mini-flow were found near constant (1.34) with and without the matrix plus TAC. According to the vaporisation studies by graphite furnace electrothermal vaporisation inductively coupled plasma atomic emission spectrometry (GF-ETV-ICP-AES), the vaporisation of Bi and Te components of the solid Bi₂TeO₅ can be completed at 1200°C in a relatively short time, ensuring a preconcentration for the Er and Nd dopants, which do not vaporise below 2200°C in an argon atmosphere. On the other hand, fast vaporisation can be performed for the analytes at 2200°C with the use of CCl₄ vapour (∼0.5 v/v%) in the internal furnace gas (Ar). It was estimated for the Er analyte that by applying 10 mg of solid sample in the GF-ETV device (dispensed into a graphite sample boat) and using a two-step heating procedure (prevaporisation of the matrix in argon and vaporisation of the analyte in a chlorinating atmosphere), the lower limit of the quantitative determination with the ICP-AES method would be approximately one order of magnitude better than attainable with the GFAAS method based on dissolution.     

Laser ablation and furnace techniques for sampling and detection in atomic emission spectrometry

Summary The potential of furnace techniques and of laser evaporation for the analysis of dry solution residues and of solids by different atomic emission procedures is described. The new one-step FANES technique (furnace atomic nonthermal emission spectrometry) is compared with the two-step procedure ETV-ICP-AES (electrothermal vaporisation—inductively coupled plasma—atomic emission spectrometry). In case of dry solution residues the sensitivity of the FANES is higher (1–2 orders of magnitude) as a result of better discharge conditions (low background) and direct sample introduction, particularly for volatile and moderately volatile substances. For refractory elements the higher gas temperature of the ICP plasma causes better atomisation, which can lead to higher sensitivity of the ETV-ICP-AES. A new Laser-FANES hybride technique is introduced for microanalysis in solid samples and compared with Laser-ICP-AES. The Laser-FANES is shown to combine the advantages of Laser-ETA-AAS (high sensitivity) and of Laser-ICP-AES (multielemental determinations), particularly for volatile and moderately volatile elements.     

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.