Electrothermal Technique Research Articles

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 Grun-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.

The use of thermal energy in ankle arthroscopy

Arthroscopy has proven to be a useful technique in the diagnosis and treatment of multiple ankle disorders. The confines of the joint, however, pose unique problems for arthroscopic instrumentation. Because of its adaptability, the electrothermal technique significantly enhances the arthroscopic approach to multiple soft tissue lesions about the ankle, including synovial disease, impingement, and instability.

Pulsed electrothermal technique for measuring the thermal diffusivity of dielectric films on conducting substrates

A simple technique for measuring the thermal diffusivity of dielectric films on thermally sinking substrates is proposed and demonstrated. It is an outgrowth of the thermal pulse technique for measuring charge and polarization profiles. The thermal diffusivity is derived from the transient electrical response induced by a thermal pulse applied to a dc voltage-biased sample. Because the response is proportional to the bias voltage, the signal-to-noise ratio is adjustable independently of the thermal pulse energy and may be made as large as required for determining the diffusivity with high precision. Measuring times of around 1 ms or shorter are sufficient for polymers with thicknesses up to 10 μm. Experimental results for two different polyimide films spin coated on crystalline silicon substrates are presented and discussed.

The separation of 99Tc from low and medium-level radioactive wastes and its determination by inductively coupled plasma mass spectrometry

A chemical separation method has been developed for the determination of 99Tc in various types of radioactive wastes. Such a method includes (i) fusion with NaOH, (ii) extraction in a column containing methyltrioctylammonium chloride, (iii) extraction by solvent with N-benzoyl- N-phenylhydroxylamine and, (iv) measurement by inductively-coupled plasma mass spectrometry (ICP-MS). From the performance standpoint, the recovery of 99Tc, using 99mTc as a yield tracer, is higher than 70%. This analytical method, as developed, ensures effective decontamination with respect to the radionuclides, insofar the decontamination factors are greater than 10 +5, whenever the residual activity may be measured. Taking into account a 3σ counting error, the detection limit obtained with the ICP-MS technique is 1.9 mBq/ml; the method enabling hence to detect activities as low as 0.3 Bq/g, with analysed samples of 0.2 g and a radiochemical yield of 70%. Studies have been dedicated to the 99Tc measurement, using the electrothermal vaporization ICP-MS technique, which lowers the detection limit by a factor 10, with the standard solution (0.3 pg/ml), compared with the previous ICP-MS technique.

Hepatic retention of copper and selenium in primary sclerosing cholangitis.

Previous studies have suggested abnormal copper metabolism in patients with primary sclerosing cholangitis (PSC). In the present work the trace element metabolism was studied in a group of 32 patients with PSC. Hepatic copper and selenium concentrations were determined with a sensitive electrothermal atomic absorption technique. Serum concentrations of copper and zinc were determined by conventional atomic absorption. For the patient group serum copper values (20.3 +/- 4.5 mumol/l) were higher than those for the control group (14 +/- 3 mumol/l), and average hepatic copper concentrations were greater by a factor of four. Serum selenium values were slightly lower, although the average hepatic selenium was significantly higher than in the healthy control group. Previous studies have discussed possible toxic effects of hepatocellular copper accumulation, which may be accompanied by formation of activated oxygen species and depletion of glutathione. In the present study, however, it could not be demonstrated that the concentration of the lipoperoxidation product, malonic dialdehyde, was higher than normal in blood. Furthermore, blood concentrations of glutathione and glutathione peroxidase were not abnormal. Although a protective effect of the raised selenium concentrations in the liver might be discussed, it is apparent that the copper accumulation in the liver cells described here did not induce detectable changes in the indices studied.

Separation of analyte and matrix for the direct analysis of high-purity molybdenum-based materials by electrothermal atomic spectrometry methods—I: Radiotracer investigation of thermal extraction of impurities in a graphite cup

By means of radiotracers, thermal vaporization of a number of detrimental trace elements (alkali, alkali earth and heavy metals) from metallic molybdenum powder has been studied. For this purpose, molybdenum samples labelled with appropriate radiotracers of the trace elements were prepared from a slurry of molybdenum oxide, ammonium molybdate solution and a radiotracer solution. Vaporization yields were measured after electrothermal treatment of the samples at temperatures between 1900 and 3000°C. Alkali and alkali earth elements, copper and zinc were vaporized with yields higher than 98%. Possible application of the electrothermal vaporization technique to the direct analysis of high-purity molybdenumbased materials by atomic absorption and atomic emission spectrometry is discussed.

Influence of thermopolar processing on the electrophysical properties of anodic tantalum oxide

We have studied the physical mechanisms which lead to failure of Ta-Ta2O5-Al thin film capacitors during prolonged exposure to an electric field and elevated temperature. Using a thermally stimulated depolarization technique we have determined the energy spectrum of the point defect levels in the band gap of the oxide in the original structure and in that subjected to fields at high temperature. The changes observed demonstrate an increase in the shallow trap and donor concentration at the interface between the oxide and the external electrode. The transition layer which develops reduces the barrier at the Al-Ta2O5 interface, leading to increased injection and, as a result, to increased conductivity. It is shown that the stability of the structure depends on the deposition technique used for the metallic layers: an electrothermal technique yields a more stable structure than a magnetron.

Aluminum contamination of infant formulas.

This study aims to determine the extent of aluminum (Al) contamination in whole milk, milk formulas, and other nutrient products commonly used for infants. Similar products from different manufacturers and different lots were measured for Al using electrothermal atomic absorption technique. Aluminum measurements were made directly from the samples or after reconstitution or dilution with Al-free water. Aluminum content was lowest (less than 50 micrograms/liter) in human milk, whole cow milk, and products that appear to require minimal manufacture processing and have few additives such as skim milk, cow milk with 2% fat, bottled glucose water, and sterile water. Highest Al levels (up to 2346 micrograms/liter) were found in highly processed and modified formulas including soy formula, preterm infant formula, and formulas for specific metabolic disorders. Aluminum content of humanized cow milk formula and bottled glucose-electrolyte solution were between the two ranges and usually less than 400 micrograms/liter. There were no significant differences in Al content of similar products from different manufacturers. Liquid formula stored in glass bottles has highest Al content compared to that stored in steel cans or powder preparation of the same product (p less than 0.05). Thus there are marked differences in Al loading depending on the type of formula, whether it is a powder or liquid preparation and the type of storage container. We speculate that raw materials such as soybean, additives such as calcium and phosphorus, manufacturing processes and storage containers are potential sources of contamination of infant formulas.

Studies in the determination of lead isotope ratios by inductively coupled plasma mass spectrometry

The application of ICP-MS to the determination of lead isotope ratios in geological materials is described. Data presented for a series of lead mineral concentrates are compared with reference values obtained by conventional solid source thermal ionisation mass spectrometry. The simultaneous determination of lead isotope ratios and trace elements is carried out in a rapid analysis mode. The application of an electrothermal vaporisation technique for small solution aliquots is described. Lead isotope ratio data for the United States Geological Survey standard reference silicate rock BCR-1, obtained without separation of lead from the matrix, are compared with previously published values obtained after separation.

Modification of a commercial electrothermal vaporisation system for inductively coupled plasma spectrometry: evaluation and matrix effects

The development and analytical utility of an electrothermal vaporisation technique (ETV) employing a Perkin-Elmer HGA-500 graphite furnace for sample introduction into the inductively coupled plasma (ICP) are assessed. Evaluation of a novel configuration with custom graphite cuvettes is described. Operational characteristics, including the effect of the length of the transport tube to the ICP torch, vaporisation temperature, carrier argon flow-rate, observation height above the coil and plasma power, are investigated. Detection limits for Be, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn ranged from 0.6 to 20 ng ml–1 with precision varying from 1.2 to 8.5% RSD at 300 ng ml–1(3 µl). The effects of major biological matrix constituents (Ca, Fe, K, Mg, Na and P) on the determination of trace elements by ETV-ICP is also investigated. Significant enhancement and/or suppression of the analyte emission is observed.

Graphite-furnace AAS with ultrasonic nebulization

A technique combining ultrasonic nebulization of solutions and graphite-furnace atomic-absorption spectrometry is described. The analytical possibilities of two different techniques are shown. In one the nebulized samples are continuously introduced into a graphite tube operated at constant temperature, and in the other deposited on the inner wall of the graphite tube and heated discontinuously. The method chosen influences the absorption values for several elements. The sensitivity for determination by continuous sampling lies between the values for the normal electrothermal AAS injection technique and flame AAS. Higher sensitivities are obtained with the deposition technique.

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.

The AAS determination of copper and zinc levels in the serum of hemodialysis patients

An electrothermal atomic absorption technique for the determination of subnanogram amounts of copper and zinc in aqueous and blood serum matrices has been evaluated. The technique has been utilized to study the effect of dialysis (artificial kidney) on the levels of these trace elements in the serum of hemodialysis patients. The present results confirm a previous study (1) which was conducted on representative samples that were taken from the continuous flow of the dialysis fluid (dialysate). Matrix effects have been minimized by using serum controls (obtained from a pool made of the tested serum samples), small sample size, and background correction. Before dialysis, values of copper for patients who were dialysed against tap water (tap-water patients) and distilled water (distilled-water patients) were: (mean +/- SD) 1297 +/- 59 and 1064 +/- 137 micrograms/L, respectively; after dialysis: 1539 +/- 98 and 1120 +/- 129 micrograms/L, respectively. Zinc levels were less affected by the dialysis process; before dialysis: tap-water patients, 952 +/- 131 micrograms/L; distilled-water patients, 932 +/- 119 micrograms/L; after dialysis: 1001 +/- 137 micrograms/L, and 934 +/- 121 micrograms/L, respectively. Because the method is sensitive, accurate, and precise, it can be utilized to study trace levels of copper and zinc in serum when limitations of sample volume exist as in the present case or with pediatric patients.

Studies on the occurrence of atoms and molecules of aluminum, gallium, indium and their monohalides in an electrothermal carbon furnace

Molecular absorption spectra of monohalides (MX; X = F, Cl and Br) of aluminum, gallium and indium have been observed, where the monohalide species were produced in the electrothermal carbon furnace. In the spectra, some characteristic band structures have been identified for each metal halide. Generally, aluminum halides and/or metal fluorides provided clear and sharp band structures. The spectral bandwidth, background absorptions, and co-existing cations influenced the analytical features of molecular absorption spectrometry utilizing the monohalide bands. The time-dependent signal profiles of atoms and molecules at the stage of atomization in the carbon furnace have been observed for discussing the mechanisms of atomization and molecule formation of the Group III elements. Alkali and alkaline earth ions enhanced the molecular absorptions of monohalides, and transition metal ions reduced the background absorptions due to cutting the oxide. In addition, the application of the molecular absorptions of monohalides to the determination of trace halogens has also been investigated using the electrothermal vaporization technique.

High frequency electrothermal technique of rock cutting. In Russian

High frequency electrothermal technique of rock cutting. In Russian

A dynamic electrothermal analysis technique based on dielectric measurements

A dynamic electrothermal analysis technique is described, which utilizes dielec- tric measurements for materials characterization. With milligram amounts of sample, both capacitance and dissipation factor are measured continuously and automatically as a function of temperature in a range from —190 to 500°C. Thus, dielectric properties are used for analysis in a way similar to differential thermal analysis. Some applications of this technique are illustrated.

Carbon disulphide synthesis by the electrothermal fluid bed technique

Carbon disulphide synthesis by the electrothermal fluid bed technique

Thermal impedance of ceramic packages using beam-lead IC chips : N. E. Hardsick, Proc. IEEE57, No. 9, September (1969), p. 1616

A three-dimensional analytical approximation for the thermal impedance of a beam-lead IC package is obtained by calcu- lating the thermal resistance of the individual elements and solving by the electrothermal analog technique. For a single chip package, thermal impedance values are presented for both a centrally located 0.005 inch diameter junction area and a source evenly distributed over the active surface of the chip under the following meunting condi- tions: a) package with external leads heat-oinked; b) package with ceramic base heat-sinked; c) chip thermally isolated on AI,O, sub- strate. Also, variations in the thermal impedance of the package with changes in the chip component dimensions are shown graphically. For arrays of beam-lead chips on small ceramic substrates, curves are presented for the upper and lower boundaries of maximum chip power as a function of the number of chips appliqued to the sub- strate. The results indicate that the relatively low power levels which are characteristic of most logic-type beam-lead devices create no thermal problems when packaged individually. However, for large chip arrays the ability of a particular substrate to dissipate the heat generated may be a limiting factor even for these seemingly insignificant power levels?

Thermal impedance of ceramic packages using beam-lead IC chips

A three-dimensional analytical approximation for the thermal impedance of a beam-lead IC package is obtained by calculating the thermal resistance of the individual elements and solving by the electrothermal analog technique. For a single chip package, thermal impedance values are presented for both a centrally located 0.005 inch diameter junction area and a source evenly distributed over the active surface of the chip under the following mounting conditions: a) package with external leads heat-sinked; b) package with ceramic base heat-sinked; c) chip thermally isolated on Al 2 O 3 substrate. Also, variations in the thermal impedance of the package with changes in the chip component dimensions are shown graphically. For arrays of beam-lead chips on small ceramic substrates, curves are presented for the upper and lower boundaries of maximum chip power as a function of the number of chips appliqued to the substrate. The results indicate that the relatively low power levels which are characteristic of most logic-type beam-lead devices create no thermal problems when packaged individually. However, for large chip arrays the ability of a particular substrate to dissipate the heat generated may be a limiting factor even for these seemingly insignificant power levels.

Thermal impedance of ceramic packages using beam-lead IC chips

A three-dimensional analytical approximation for the thermal impedance of a beam-lead IC package is obtained by calculating the thermal resistance of the individual elements and solving by the electrothermal analog technique. For a single chip package, thermal impedance values are presented for both a centrally located 0.005 inch diameter junction area and a source evenly distributed over the active surface of the chip under the following mounting conditions: a) package with external leads heat-sinked; b) package with ceramic base heat-sinked; c) chip thermally isolated on Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> substrate. Also, variations in the thermal impedance of the package with changes in the chip component dimensions are shown graphically. For arrays of beam-lead chips on small ceramic substrates, curves are presented for the upper and lower boundaries of maximum chip power as a function of the number of chips appliqued to the substrate. The results indicate that the relatively low power levels which are characteristic of most logic-type beam-lead devices create no thermal problems when packaged individually. However, for large chip arrays the ability of a particular substrate to dissipate the heat generated may be a limiting factor even for these seemingly insignificant power levels.