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).     

Interface for capillary electrophoresis coupled with inductively coupled plasma atomic emission spectrometry.

A modified concentric nebulizer was used as the interface to couple capillary electrophoresis (CE) to inductively coupled plasma atomic emission spectrometry (ICP-AES). The CE capillary replaces the central tube of the concentric nebulizer. The tip of the nebulizer tapers slowly to allow uncertainty in the position of the capillary. A platinum wire was inserted into the CE capillary to provide electrical connection to the CE power supply. pH changes inside the capillary due to electrolysis of the background buffer electrolyte was small and has minimal effects on the CE separation. The peak broadening effects due to the nebulizing gas flow, however, were significant. Resolution decreases quickly when the flow-rate of the carrier gas increases. Sample stacking technique was used to improve the resolution of species of opposite charge, e.g., Cr(VI) vs. Cr(III) ions. Detection limit of Cr based on peak area is approximately 10 ppb for the CE-ICP-AES system.     

An electronic aid for line selection for scanning inductively coupled plasma atomic emission spectrometers

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). Accompanying this hard copy text is a disk containing the program, source flies, data files and a brief manual along with a few programming notes. The main article discusses the purpose of this work, and the Appendix provides brief instruction on the use of the program, manipulation of the data, and source code. An automatic file selection system for the control of a rapid scanning spectrometer performing atomic emission spectrometry has been developed using the PROLOG language. The system can be “taught” the elemental composition of a given sample type. It uses this information (when available) to generate a linear search strategy which minimizes the number of lines that need to be measured. The rules used by the system can be observed during system operation to allow a trace of the logic. Reading of the initial data base takes no more than 6 s and then decisions are made in less than 1 s per line.     

A systematic approach to optimum working conditions with inductively coupled plasma atomic emission spectrometry

Optimum experimental factors were determined for the analytical determination of Al, Cd, Fe, Pb, and Zn by ICP atomic emission spectrometry. Based on systematically determined factor levels, working conditions were found that gave similiar, and sometimes better results compared with the hitherto used levels of factors. All measurements were performed with a sampling time of 150 ms as often used in routine analysis in the laboratory. This optimization resulted in a reduced outer plasma gas flow from 15 L/min argon to 12 L/min without any relevant changes of the achievable detection limits. A serious problem was that only one analytical line of Al could be used. A comparison with the lower limit of application (comparable with the detection limit) from German directive DIN 38406, part 22 ([1]), showed that the detection limits of Al and Fe are superior, whereas for Cd there was only little improvement. The detection limits of Zn and especially Pb are always higher than the lower range of application under these conditions. Therefore, the use of two device-parameter sets for hard and soft lines, respectively, is strongly suggested. Maps with the observed signal-to-noise-ratios were systematically acquired for each element analyzed in connection with different strategies for optimum search.     

A systematic approach to optimum working conditions with inductively coupled plasma atomic emission spectrometry

Optimum experimental factors were determined for the analytical determination of Al, Cd, Fe, Pb, and Zn by ICP atomic emission spectrometry. Based on systematically determined factor levels, working conditions were found that gave similar, and sometimes better results compared with the hitherto used levels of factors. All measurements were performed with a sampling time of 150 ms as often used in routine analysis in the laboratory. This optimization resulted in a reduced outer plasma gas flow from 15 L/min argon to 12 L/min without any relevant changes of the achievable detection limits. A serious problem was that only one analytical line of Al could be used. A comparison with the lower limit of application (comparable with the detection limit) from German directive DIN 38406, part 22 ([1]), showed that the detection limits of Al and Fe are superior, whereas for Cd there was only little improvement. The detection limits of Zn and especially Pb are always higher than the lower range of application under these conditions. Therefore, the use of two device-parameter sets for hard and soft lines, respectively, is strongly suggested. Maps with the observed signal-to-noise-ratios were systematically acquired for each element analyzed in connection with different strategies for optimum search. mon compromise condition (combined analysis) and the limits of quantification demanded in the German directive DIN 38406, part 22 [1]. Only four, but the most important, experimental factors were changed, the other experimental factors were always kept constant (Tables 1 and 2).     

Modified Babington nebulizer for inductively coupled plasma atomic emission spectrometry.

A PTFE Babingtonnebulizer equipped with a hood was investigated for inductively coupled plasma atomicemission spectrometry in conjunction with a PTFE cyclone chamber, in order to nebulize various sample solutions containing high salts, hydrofluoric acid and/or suspended solid. A hood of 3 mmphi (nozzle side) - 5 mmphi (outlet side) and 6 mm in length gave a comparable or higher sensitivity compared to a system with a commercially available concentric nebulizer and a glass cyclone chamber. Moreover, the present nebulizer was fully interchangeable with a concentric one at normal argon pressure, attaining sufficient stability, a short wash-out time and good nebulizing of high matrices solutions. The present system was successfully applied to the determination of trace impurities in highly pure silica powders.     

Quality of calibration in inductively coupled plasma atomic emission spectrometry

Calibration is a crucial step during the whole analytical process. A procedure is suggested to assess the quality of linear regression used for the calibration graph, based on the use of confidence limits for the concentration, as the regression coefficient is not appropriate for this purpose. This procedure has been applied to inductively coupled plasma atomic emission spectrometry. It indicates that the use of only three standards should be discouraged because of unacceptably high confidence limits for the concentration. Moreover, use of weighted regression is more adequate in performing the least squares method and provides more constant confidence limits over the concentration range used to construct the calibration graph. This procedure could be easily added to any commercially available ICP system software.     

Carbon-related matrix effects in inductively coupled plasma atomic emission spectrometry

In Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), it has been observed that the emission intensity of some atomic lines is enhanced or depressed by the presence of carbon in the matrix. The goal of this work was to investigate the origin and magnitude of the carbon-related matrix effects in ICP-AES. To this end, the influence of the carbon concentration and source (i.e. glycerol, citric acid and potassium hydrogen phthalate), the experimental conditions and sample introduction system on the aerosol characteristics and transport, plasma excitation conditions and the emission intensity of several atomic and ionic lines of a total of 15 elements has been studied. Results indicate that carbon related matrix effects do not depend on the carbon source and they become more severe when the amount of carbon loaded into the plasma increases, i.e., when using: (i) carbon concentrations higher than 5 g L^− 1; (ii) high sample uptake rates; and (iii) efficient sample introduction systems. Thus, when introducing carbon into the plasma, the emission intensity of atomic lines with excitation energies below 6 eV is depressed (up to 15%) whereas the emission intensity of atomic lines of higher excitation energies (i.e. As and Se) are enhanced (up to 30%). The emission intensity of the ionic lines is not affected by the presence of carbon. The origin of the carbon-related interferences on the emission intensity of atomic lines is related to changes in the line excitation mechanism since the carbon containing solutions show the same aerosol characteristics and transport efficiencies as the corresponding aqueous solutions. Based on the previous findings, a calibration approach for the accurate determination of Se in a Se-enriched yeast certified material (SELM-1) has been proposed.     

Spectrum stripping in rapid sequential atomic emission spectrometry with the inductively coupled plasma

Rapid sequential atomic emission spectrometry with the ‘Zig Zag’ acquisition system (ISA Jobin Yvon, France) in the case of the inductively coupled plasma is described. The ‘Zig Zag’ system is shown to enable the application of spectral stripping, as both the reproducibility of the intensities measured, for several lines of Fe, and the reproducibilty of the wavelength positioning (errors below 3 pm in the 2nd order and 5 pm in the 1st order) were found to be high. Using an integration time of only 2.5 ms/point, the precision of the intensities expressed as the relative standard deviation is below 5%. These features are shown to allow spectrum stripping from the contribution of a Zr matrix, which has a rather line-rich atomic emission spectrum. Spectrum stripping was applied in the wavelength range from 237.9 to 241.1 nm, where 10 of the most sensitive emission lines of Fe were found. For sample solutions with 500 mg/l Zr only, 10 mg/l Fe only, 500 mg/l Zr as well as 10 mg/l Fe, and for a blank solution, respectively, five spectral scans were averaged and the averaged spectral scan for a blank solution was subtracted. The spectral scan obtained for a solution containing 500 mg/l Zr only was subtracted from the one obtained for the solution containing both 500 mg/l Zr and 10 mg/l Fe. The result of spectral stripping is comparable to the experimentally obtained spectral scan for the solution containing 10 mg/l Fe only after blank subtraction. The recovery for Fe was found to be 93±2% and is therefore comparable to the one obtained by chemical separation methods using solvent extraction. When using an integration time of 50 ms per measurement point instead of 0.5 ms/point, as it is possible in the case of the ‘Zig Zag’ approach, the detection limit for Fe in the measurement solutions can be improved from 20 down to 3 μg/l, or from 40 to 6 μg/g Zr, respectively.     

A factor analysis approach to optimized line selection in inductively coupled plasma atomic-emission spectrometry

The best analytical line for determination of a specified analyte is selected from a set of lines on the basis of the least interference in a particular sample matrix, by several cycles of mathematical analysis. Unsuitable lines are rejected in the first few cycles, the best lines being retained until last. A multivariate analysis after each cycle provides an updated estimate of the analyte concentration. This process is performed without reference to spectral tables.     

Line selection and interference correction for the analysis of tungsten alloy by inductively coupled plasma atomic emission spectrometry

A method for the analysis of tungsten alloy to determine selected elements using inductively coupled plasma atomic emission spectroscopy is described, with emphasis on line selection and spectral interference. The spectral interference coefficients were calculated for the spectral lines of selected major and trace elements. These values were used to select analytical lines and to calibrate concentrtions of the analytes. The detection limits of the elements for this method were determined and compared with those obtained by flame atomic absorption spectrometry and direct current carbon are emission spectrometry. The results indicated that the detection limits for all of the elements determined by the proposed method are significantly better than those obtained by other techniques. In this study, the analytical reliability of the proposed method was estimated by comparison of the analytical data for the two types of tungsten alloys produced by the Korean Tungsten Company with those obtained by the matrix matching method and the results indicated that the accuracy of multi-element analysis is satisfactory.     

Microwave desolvation for acid sample introduction in inductively coupled plasma atomic emission spectrometry

This study deals with the behaviour of a microwave desolvation system (MWDS) with acid solutions in inductively coupled plasma atomic emission spectrometry. Hydrochloric, nitric, sulphuric and perchloric acids at different concentrations (up to 0.6 mol l⁻¹) have been tested. Sample uptake rate (Q_l) was also varied. The parameters evaluated for each variable were analyte and solvent transport rates and emission intensity. The combination of low acid concentrations (0.05–0.1 mol l⁻¹) and low liquid flows (0.4 ml min⁻¹) leads to the highest analyte transport rate and emission signal and to the lowest solvent transport rate. For Q_l higher than 1.9 ml min⁻¹, the use of an impact bead is advisable. Among the acids tested, sulphuric and perchloric acids give rise to higher emission intensities than hydrochloric acid and nitric acid. Nonetheless, the limits of detection (LODs) obtained with the MWDS are about the same magnitude irrespective of the solution employed. The LODs reached when using the MWDS are similar to those obtained with a desolvation system based on infrared heating of the aerosol.     

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.     

Bulk analysis by IR laser ablation inductively coupled plasma atomic emission spectrometry

Two laser ablation systems dedicated to bulk analysis were evaluated for steel and PVC samples, using inductively coupled plasma atomic emission spectrometry detection. These systems were characterized by the use of a Nd:YAG laser operating at 1064 nm, the absence of observation device and a large laser spot size. The 1064 nm wavelength was selected to avoid the use of frequency-multiplying optics, and to be less critical to the sampling position. Calibration graphs and limits of detection are given for both types of materials. LODs were in the range 3-120 microg/g for steel, and in the range 0.07-15 microg/g for PVC. In the case of steel samples, similar calibration graph slopes were obtained between polished and unpolished samples.     

Correlation study of internal standardization in inductively coupled plasma atomic emission spectrometry

Correlation studies (calculation of the cross-correlation function and correlation coefficients) were carried out between fluctuations in the emission signals from various analyte and internal standard elements. Some statistics are presented which may help give a clearer picture of the utility of the internal standard principle. Improvements in precision brought about by the use of suitable standards are in the region of a factor of two. The use of argon emission lines as internal standards does not prove effective as an inverse correlation is observed between the emission of these lines and analyte lines.     

Enhancement effect of organic solvents in inductively coupled plasma atomic emission spectrometry

Summary The enhancement factors of various organic solvents in inductively coupled plasma atomic emission spectrometry (ICP-AES) were measured for diethyldithiocarbamate-cadmium(II) or mercury(II)-solvent systems by comparing the maximum emission intensity of an extract with that of the corresponding aqueous solution. The correlation between the enhancement factors obtained and physical parameters of the solvents were investigated. Among them, the best inverse linear relationship existed between log dielectric constant and log enhancement factor. The plot of log (boiling point x viscosity) vs. log enhancement factor also resulted in a line with a negative slope except water. Carbon tetrachloride, chlorofom and xylene, which gave much larger enhancement factors, were recommended for the use in ICP-AES.

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Verstärkungseffekt durch organische Lösungsmittel in der ICP-AES

     

Determination of the ZnGeP2 composition by inductively coupled plasma atomic emission spectrometry

A procedure employing inductively coupled plasma atomic emission spectroscopy has been developed for the precise determination of the composition of Zn_{1 + x}Ge_{1 + x}P_{2 + x} alloys after their autoclave digestion. An optimal composition of the acid mixture has been chosen and the conditions preventing element losses in the digestion process have been found. To minimize the error of the developed procedure, the optimal concentration of Zn, Ge, and P in the analytes was found by calculating the results of analysis as atomic ratios Zn : Ge and P : Ge. The accuracy of the developed procedure was confirmed by the standard addition method and the comparison of the results with the results of an independent method. The relative standard deviation of the determination of atomic ratios was 0. 7–2.0%.     

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.     

Sulfur analysis of conifer needles by inductively coupled plasma atomic emission spectrometry

Zusammenfassung Nadelproben werden in einem Druckaufschlu\gefÄ\ mit SalpetersÄure aufgeschlossen und die erhaltenen Lösungen mittels ICP-AES auf Schwefel analysiert. Die Messung erfolgt bei 182,04 nm in einem mit Stickstoff gespülten Spektrometer. Die Ergebnisse korrelieren gut mit unabhÄngigen Bestimmungen durch Wickbold-Aufschlu\ und Ionen-Chromatographie. Das Verfahren hat den Vorteil, da\ keine Verluste des Analysenelements auftreten und da\ die Aufschlu\lösung auch für die simultane Bestimmung von Spurenmetallen mit der ICP-AES geeignet ist.