Direct analysis of fly ash materials by inductively coupled plasma atomic emission spectrometry using slurry nebulization

Fly ash samples of cement works were analysed using slurry nebulization inductively coupled plasma atomic emission spectrometric (ICP-AES). Because of the influence of the experimental factors on the signal intensity, the optimal conditions of the analysis circumstances were determined. Control analyses (wet digestion followed by ICP-AES, and XRF of dry powders (pressed pellets)) were also carried out to compare the results. Based on the result, it was concluded that the slurry nebulization method using slurry standard of same type reference material for calibration can be applied for rapid but less precise (RSD 5–10%) determination of the elements in fly ash.     

Modelling of the evaporation behaviour of particulate material for slurry nebulization inductively coupled plasma atomic emission spectrometry

This paper is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta, Part B (SAB). This hardcopy text, comprising the main body and an appendix, is accompanied by a disk with programs, data files and a brief manual. The main body discusses purpose, design principle and usage of the computer software for modelling the evaporation behaviour of particles in inductively coupled plasma atomic emission spectrometry (ICP-AES). Computer software has been developed in FORTRAN 77 language in order to simulate the evaporation behaviour of particles of refractory materials such as encountered in the analysis of advanced ceramic powders by slurry nebulization inductively coupled argon plasma atomic spectrometry. The program simulates the evaporation of single particles in the inductively coupled plasma and also enable it to calculate on the base of a given particle size distribution the evaporation behaviour of all the particles contained in a sample. In a so-called “intensity concept”, the intensity is calculated as a function of the observation height in order to determine recovery rates for slurries compared with aqueous solutions. This yields a quick insight whether a calibration with aqueous solutions can be used for analysis of slurries of a given powder by slurry nebulization ICP-AES and also is a help in determining the optimal parameters for analyses of powders by means of slurry nebulization ICP-AES.Applications for the evaporation of Al₂O₃ and SiC powders document the usefulness of the model for the case of a 1.5 kW argon ICP of which the temperature at 8 mm above the load coil has been determined to be 6100 K. The model predicts the maximum particle size for SiC and Al₂O₃ that can be transported (10–15 μm) and evaporated for a given efficiency under given experimental conditions. For both Al₂O₃ and SiC, two ceramic powders of different grain size were investigated. The median particle sizes cover the range typical of ceramic powders. Investigations were made for SiC A 10 (median particle size 2.2 μm), SiC F1200 (4.3 μm) and Al₂O₃ AKP 30 (< 1.9 μm) and Al₂O₃ Cilas 715 (3.0 μm), respectively, in which particles with diameters of up to 23 μm still are found.     

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.     

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     

Determination of selenium in blood serum by inductively coupled plasma atomic emission spectrometry with pneumatic nebulization

The possibility of determining selenium in blood serum using inductively coupled plasma emission spectrometry with conventional pneumatic nebulization was studied. A high-resolution spectrometer (SBW=6 pm) with laterally viewed ICP was employed. Analysis with conventional pneumatic nebulization could overcome laborious and demanding digestion, which is necessary for hydride generation. A pressure digestion with nitric acid at 160 degrees C was sufficient to decrease the carbon content in the serum sample to 5%-10% of its original value. Spectral interference of the CN band was observed and mathematically corrected. It was found that the carbon-induced selenium line emission enhancement occurred even under ICP optimized conditions. A method of determination was developed and applied to the analysis of blood serum. True limit of detection in real samples is 0.01-0.02 mg/L and the limit of quantification (RSD 10%) is 0.03-0.07 mg/L using Se I 196.090 nm line at an integration time of 10-2 s. The method was tested by analysis of porcine blood serum and the serum reference material Seronorm MI 0181.     

Direct determination of impurities in high purity silicon carbide by inductively coupled plasma optical emission spectrometry using slurry nebulization technique

A novel method for the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni and Ti in high purity silicon carbide (SiC) using slurry introduction axial viewed inductively coupled plasma optical emission spectrometry (ICP-OES) was described. The various sizes of SiC slurry were dispersed by adding dispersant polyethylene imine (PEI). The stability of slurry was characterized by zeta potential measurement, SEM observation and signal stability testing. The optimal concentration of PEI was found to be 0.5 wt% for the SiC slurry. Analytical results of sub-μm size SiC by the slurry introduction were in good accordance with those by the alkaline fusion method which verified that determination could be calibrated by aqueous standards. For μm size SiC, results of most elements have a negative deviation and should be calibrated by the Certified Reference Material slurry. Owing to a rather low contamination in the sample preparation and stability of the slurry, the limits of detection (LODs), which are in the range of 40-2000 ng g⁻¹, superior to those of the conventional nebulization technique by ICP-OES or ICP-MS.     

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).     

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.     

Experimental studies for the characterization of analytical performance in axially-observed inductively coupled plasma atomic emission spectrometry

Investigations were carried out on the optimization of excitation and projection conditions of the axially-observed inductively coupled plasma (ICP) concerning simultaneous measurements. For minimized background equivalent concentration (BEC) it can be shown that the optimal excitation conditions of the atomic and ionic lines also vary in the case of axial plasma observation. A relationship was confirmed between the high frequency power and the excitation energy of the analytical lines. The main contribution of this work is the displacement of the axial viewing inductively coupled plasma by means of an x,y,z sliding carriage.The displacement showed that under the selected experimental conditions the point of observation is spatially identical for all analytical lines. Received: 30 May 1997 / Revised: 20 November 1997 / Accepted: 25 November 1997     

Experimental studies for the characterization of analytical performance in axially-observed inductively coupled plasma atomic emission spectrometry

Investigations were carried out on the optimization of excitation and projection conditions of the axially-observed inductively coupled plasma (ICP) concerning simultaneous measurements. For minimized background equivalent concentration (BEC) it can be shown that the optimal excitation conditions of the atomic and ionic lines also vary in the case of axial plasma observation. A relationship was confirmed between the high frequency power and the excitation energy of the analytical lines. The main contribution of this work is the displacement of the axial viewing inductively coupled plasma by means of an x,y,z sliding carriage.The displacement showed that under the selected experimental conditions the point of observation is spatially identical for all analytical lines. Received: 30 May 1997 / Revised: 20 November 1997 / Accepted: 25 November 1997     

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.     

Mixed-gas inductively coupled plasma atomic emission spectrometry using a direct injection high efficiency nebulizer

Experimental studies and computer simulations were conducted to identify plasma operating conditions and to explore and contrast the excitation conditions of Ar, Ar-O2, and Ar-He inductively coupled plasmas (ICPs) for the introduction of microliter volumes of sample solutions with a direct injection high efficiency nebulizer (DIHEN). The best MgII 280.270 nm/MgI 285.213 nm ratio (6.6) measured with Ar ICP atomic emission spectrometry for the DIHEN (RF power = 1500 W; nebulizer gas flow rate = 0.12 L min(-1)) was less than the ratio (8.2) acquired on the same instrument for conventional nebulization (1500 W and 0.6 L min(-1)). Addition of small amounts of O2 or He (5%) to the outer gas flow improved excitation conditions in the ICP, that is, a more robust condition (a MgII/MgI ratio of up to 8.9) could be obtained by using the DIHEN with Ar-O2 and Ar-He mixed-gas plasmas, thereby minimizing some potential spectroscopic and matrix interferences, in comparison to Ar ICPAES.     

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.     

Laser ablation inductively coupled plasma atomic emission spectrometry of a uranium-zirconium alloy: ablation properties and analytical behavior

The ablation properties and analytical behavior of a uranium-zirconium alloy have been examined using tandem laser ablation/pneumatic nebulization sample introduction in conjunction with inductively coupled atomic emission spectrometry (LA-ICP-AES). An apparent change in composition of the laser ablation aerosol (1–15 GW cm⁻² Zr deficient, 40–250 GW cm⁻² Zr rich) is observed. This phenomenon is independent of laser wavelength. After collection and bulk chemical analysis of the ablation product, this phenomenon is attributed to an atomization interference in the ICP.

Two distinct modes of laser ablation have been observed which depend upon the wavelength of the ablating laser (visible or near infrared). These two modes result in characteristic ablation crater types and analyte emission behavior. Ablation yields at 1064 nm are dependent upon laser power density only, whilst yields at 532 nm are dependent upon both laser power density and illumination area. The latter is considered to be symptomatic of direct interaction of the laser light with the surface, and the former, of indirect coupling of laser energy, via a micro-plasma, into the surface.     

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 arsenic in plant samples by inductively coupled plasma atomic emission spectrometry with ultrasonic nebulization: a complex problem

Under well-defined conditions, the analysis of most trace elements by inductively coupled plasma atomic emission spectrometry with ultrasonic nebulization (ICP-AES-USN) leads to accurate results for environmental matrices usually studied. Due to differences in matrix composition between standards and samples, ICP-AES-USN determinations of arsenic are interfered with by changes that take place mainly within the desolvation stage of the USN device. In this work, effects of plant matrices on the determination of As in six arsenic species have been investigated. Firstly, interferences were simulated by measuring analyte (species) signals in solutions containing variable concentrations of the main matrix elements encountered in mineralized plant samples (K, Ca, Mg, P and Na). Secondly, the influence of real plant matrices on emission signals of arsenic species was also studied. In this case, the observed effects were different than for individual matrix elements considered separately: Ca and Mg always present in real samples efficiently compensate the undesirable effects. Validation of this statement has been performed using mineralized plant reference materials. In addition, ICP-AES-USN results have been compared with those obtained by Zeeman electrothermal atomic absorption spectrometry.     

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.