Slurry Nebulization Research Articles

Slurry atomization using hydrogen-modified inductively coupled plasmas

The use of molecular gas addition as a volatilization aid in slurry nebulization inductively coupled plasma atomic emission spectrometry (ICP-AES) has been investigated using a combination of rigorous optimization strategies and spectrochemical measurements. The addition of hydrogen resulted in an improvement in accuracy, which corresponded to the elimination of atomization interferences observed during the analysis of a highly refractory material by slurry nebulization ICP-AES. This ability to decompose refractory particles correlated with higher rotational plasma temperatures. This increase in temperature from 2200 to 3900 K was attributed to increased energy transfer from the toroidal to the annular region of the ICP as a consequence of the higher thermal conductivity of hydrogen compared with argon. This process appears to be self-limiting and a mechanism is proposed to account for this behaviour.

Significance of generation of cation-exchange surfaces by grinding to slurry nebulization

The generation of additional cation-exchange surfaces as a consequence of grinding mineral samples is discussed, especially with respect to the successful analysis of samples using the standard additions technique with slurry atomization. The possible influence of such cation-exchange surfaces upon the functioning of chemical modifiers such as ionization buffers is briefly considered.

Electron energy-loss spectroscopy and electron probe X-ray microanalysis of exhaust aerosols in slurry nebulization inductively coupled plasma atomic spectrometry for ceramic powders

Exhaust aerosols in inductively coupled plasma (ICP) atomic spectrometry generated from different ceramic powder suspensions (Al 2O 3, ZrO 2 and SiC) were investigated by electron energy loss spectroscopy (EELS) and electron probe X-ray micro analysis (EPXMA). Differences in morphology, size and elemental composition of sub-micrometer residues of these refractory powders, collected above ICPs operated with different gasses, were found to depend on the outer gas (N 2 O 2 and Ar), the distance between the impacting stage and the plasma, and on the ceramic powder introduced as a slurry into a suitable nebulizer. Identical exhaust types of particles were observed in the case of Al 2O 2 and ZrO 2 slurries, also when different outer gases and different operation conditions were used. For SiC, much depends on the outer gas used, as shown by morphological and chemical composition studies. Electron energy loss spectroscopy and element spectroscopic imaging (ESI) were used for the elemental analysis and the localization of the detected elements (Al, Zr, Si, C, O and N) in the individual exhaust particles.

Direct analysis of slags by inductively coupled plasma atomic emission spectrometry using slurry sample introduction techniques

A practical method is described for the direct determination of Si, Ca, Mg, Al, Fe, Mn, Ti, Na and K in slag samples by the introduction of sample suspensions into the inductively coupled plasma atomic emission spectrometer. The effect of the particle size distribution on the atomization efficiency of these elements when slurries of the slag samples were aspirated into the plasma has been studied. The slurry samples were prepared by dispersing 0.1 g of ground slag in 100 ml of 0.35% ammonia solution; calibration was achieved by the use of a reference slag prepared in the same manner. The results obtained for the direct analysis of slag slurries using such a procedure were in good agreement with those obtained by classical dissolution of the sample. The reproducibility of the results with slurry nebulization (concentration range 1.7–5.5%) were poorer than those observed with aqueous solutions (concentration range 0.5–4.8%) but were acceptable for slag industrial control.

A STUDY OF SAMPLE INTRODUCTION WITH SLURRY NEBULIZATION FOR THE DETERMINATION OF IRON IN SILICON NITRIDE BY ICP-ES

Direct analysis of silicon nitride for the determination of iron by ICP-ES with slurry nebulization has been attemped. A silicon nitride sample of 0.05g-0.5g is put into a 100ml flask and diluted to the volume with 0.5% (NaPO3)6 solution. The slurry is introduced into ICP torch with a concentric nebulizer, The main operating conditions were determined by using standard silicon nitride. Particle size of the solid sample and carrier argon gas flow rate had a great influence on sensitivity and accuracy in the determination of iron.

Aerosol sizing and transport studies with slurry nebulization in inductively coupled plasma spectrometry

Droplet size distributions, analyte transport efficiencies and analyte mass transport rates were determined for a V-groove Babington type nebulizer, operated with solutions and slurries at different sample aspiration rates. Also, the effect of the impact bead was studied. For solutions and slurries, a maximum analyte transport efficiency of 1.42% and 2.50% respectively was obtained. Also, for slurries with a high concentration of dissolved salts, elemental redistribution of the solute and solid analyte over the droplets as a function of the size range was observed. The observed effect points out that the aerosol production processes are different for pure solution droplets and droplets containing particulate matter. This puts constraints on the use of solutions for calibration in slurry analysis using inductively coupled plasma spectroscopy

Application of slurry nebulization to trace elemental analysis of some biological samples by inductively coupled plasma mass spectrometry

The application of slurry nebulization/inductively coupled plasma mass spectrometry (ICP-MS) to trace elemental analysis of biological samples has been investigated. Three standard samples of the National Institute of Standards and Technology (NIST) were dispersed in 1% aqueous Triton X-100 solution by grinding with a planetary micronizing mill. The resulting slurries were nebulized into an ICP without any additional treatments. The 1% (m/v) slurry of the NIST bovine liver showed no significant influence on cone blockage and signal suppression/enhancement. Detection limit, precision and accuracy were discussed for the determination of 24 elements of interest in bovine liver, rice flour and pine needles. Detection limits ranged from 0.0001 μg g−1 for U to 0.52 μg g−1 for Zn at the effective integrating time of 10 s. For high mass elements, low blank values were obtained, yielding excellent limits (<0.01 μg g−1). Acceptable accuracy and precision were obtained for most of the elements in the NIST bovine liver and rice flour, even for the volatile elements, such as As, Se and Br. However, relatively poor accuracy was obtained for the analysis of pine needles.

Noise characteristics in inductively coupled plasma optical emission spectrometry using slurry nebulization and direct powder introduction techniques

By use of Fourier analysis, the noise sources of inductively coupled plasma optical emission spectrometry (ICP-OES) were examined for two common types of torches, a Green-field and a Fassel type torch

Rapid determination of zinc and iron in foods by flow-injection analysis with flame atomic-absorption spectrophotometry and slurry nebulization

A rapid method of determining zinc and iron in food by flame atomic-absorption spectrophotometry with slurry nebulization into an air—acetylene flame has been developed. A V-groove, clog-free Babington-type nebulizer, coupled to a single-line flow-injection analysis (FIA) system, was employed to introduce the slurry into the spray chamber. Under the FIA conditions described, an injection frequency of 120/hr is possible, with negligible carry-over and memory effects. The calibration graphs were obtained by using various concentrations (up to 0.1 g/ml) of white bean homogenate as standards, rather than solutions. The method has been applied to various kinds of foods, including grains, vegetables, fruits and sausage. Homogenization of semi-prepared samples to form slurries took only 4 min. Relative deviations between results by the slurry and solution methods for both elements averaged 2–3%. Detection limits by the slurry method were 0.3 μg/ml Zn and 0.6 μg/ml Fe.

Elemental recoveries for clay minerals analysed by inductively coupled plasma atomic emission spectrometry using slurry nebulisation

Research was undertaken to determine the effects of particle size and matrix solution composition on matrix interferences for slurry nebulisation analysis of clay minerals by inductively coupled plasma atomic emission spectrometry. Four size fractions of Grundite illite and Georgia kaolinite 3 were used for these analyses. The spectrometer was calibrated with multi-element solution standards. Elemental recoveries were determined by comparing the results obtained using slurry nebulisation with results for elemental determination from hydrofluoric acid digests of the samples. A differential effect of particle size on elemental recoveries was observed for samples prepared in HNO3 and NaCl matrix solutions. For the Grundite illite, Si and Al recoveries significantly decreased with increases in particle size, Mg and Fe recoveries decreased to a lesser extent and Ca recoveries were independent of particle size. These differences were attributed to the displacement of various amounts of Fe, Mg and Ca from clay particles into the matrix solutions by matrix solution cations and the more efficient transport of the matrix solutions than the particles to the plasma. In addition, Al recoveries were from 2 to 21% lower than Si recoveries for samples prepared in the HNO3 matrix solutions. Aluminium recoveries significantly increased with increases in observation height, which indicates that Al recoveries were limited by the incomplete dissociation -excitation of clay particles within the plasma. Furthermore, Al recoveries were significantly greater for samples prepared in 0.1 M NaCl than for samples prepared in 1 M HNO3. This effect is tentatively attributed to the enhanced collisional dissociation of clay particles. Matrix interferences may introduce substantial bias in results of slurry nebulisation analyses. This bias, however, can be minimised by restricting slurry nebulisation analyses to samples with particle sizes less than 2 µm and by using 0.1 M NaCl matrix solutions.

A study of laser ablation and slurry nebulisation sample introduction for the analysis of geochemical materials by inductively coupled plasma spectrometry

The performances of two alternative sample introduction methods for use with Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) have been evaluated for the analysis of the same sample material. The laser ablation sample introduction system is based on a Nd:YAG laser to which an x-y-z translational sampling head had been added. A study has been made of a number of parameters which affect the performance of the system to find the optimum operating conditions. The slurry introduction system involved aspirating the slurries into the plasma using a “de Galan” nebuliser and a “Scott-type” spray chamber arrangement. A study has been made of the parameters which control the production of stable homogeneous slurries. Initial particle size measurements have been carried out on the slurried samples to show how this affects this method of sample introduction. Results are presented for the analysis of a South African reference material rock sample (SARM 5) by ICP-OES with both laser ablation and slurry nebulisation sample introduction and some preliminary results for the analysis by ICP-MS with laser ablation introduction. Semi-quantitative results are obtained for laser ablation ICP-OES as only one matrix matched standard is used. However, the agreement between the results obtained for slurry nebulisation and the certificate value is poor. It is suggested by comparison with previous studies that this may be due to particle size effects. Encouraging results were obtained for the determination of trace elements by laser ablation ICP-MS.

Statistical considerations for the direct introduction of particulate samples for plasma emission and plasma source mass spectrometry

The statistical relationships for measurement uncertainties due to the discrete nature of particles in the direct analysis of powder samples with plasma sources are derived. Although the principles can be applied to direct analysis of particulates in general, the emphasis is placed on the introduction of powder samples by fluidized-bed and slurry nebulization methods. Uncertainties unique to the direct analysis of powders can be attributed to two main factors; random variation of the number of particles used for measurement, and homogeneity of the powder. Relationships for the compound uncertainty due to both these effects were derived applying Poisson and binomial distributions for binary mixtures. The compound variance is shown to be equal to the product of the average total number of panicles used for the measurement, and the fraction of particles containing the analyte in the bulk mixture.

The direct introduction of powders for plasma emission with fluidized-bed and slurry nebulization methods: particle flow rate and analyte heterogeneity

The magnitude of measurement uncertainty caused by particle sampling statistics in the direct ICP-AES analysis of powders was investigated using silica-immobilized 8-hydroxyquinoline with analyte elements spiked homogeneously and at varying degrees of heterogeneity. At panicle flow rates above 10 000 particles (25 μm diameter) per measurement, the statistical uncertainty in the number of particles (Poisson statistics) was less than uncertainty introduced from other sources. Uncertainty originating from sample heterogeneity (analyte elements distributed on a fraction of the sample particles) was over 10% when analyte was distributed on fewer than 1 in 100 particles (flow rates about 25 000 particles per measurement). The measured uncertainty in the emission of Cu agreed well with theory, other elements (Cd, Co) showed considerably higher than expected relative standard deviation. Internal standard compensation for signal noise originating from variation in the particle flow became ineffective as the sample heterogeneity increased. Measurement of emission signals of homogeneous powder samples showed an apparent level of “effective heterogeneity” which set the lower limit to which internal standardization effectively compensated for noise. Increasing the numbers of sample particles by grinding the sample to the smallest possible size is shown to be the most effective practical approach to decrease contribution of particle sampling statistics to the measurement uncertainty. Instrumental improvements which permit simultaneous measurement of analyte lines and off-peak background offer promise for reduction of measurement uncertainty.

The analysis of geological samples by slurry nebulisation inductively coupled plasma—mass spectrometry (ICP-MS)

New techniques for the analysis of geological samples by slurry nebulisation inductively coupled plasma-mass spectrometry (ICP-MS) are described. Although samples in the form of solutions are commonly used for ICP-MS analysis, many rocks and minerals are resistant to acid attack. Slurry nebulisation avoids some of the problems associated with sample digestion by introducing the sample into the ICP as a suspension of finely ground particles. Within the error of the measured data, no significant matrix effects were observed. No sample matrix matching is required and calibration can be carried out via standards prepared in the suspending agent used for the slurry preparation. Thirteen widely available reference materials were analysed for eighteen elements. These elements include those which may be lost during an open acid digestion (Se, Cr and As) and those present in insoluble mineral phases (Nb and Ta). Uranium and thorium were also included as they are difficult to analyse by other techniques. Some modifications to the standard ICP-MS operating conditions were found to be necessary. Both inter- and intra-sample precision was investigated and is considered by the authors to be adequate for routine analysis. Measured values for most elements analysed compare favourably with recommended values.

Slurry Nebulization Technique for Direct Determination of Rare Earth Elements in Silicate Rocks by Inductively Coupled Plasma Mass Spectrometry

Direct analysis of silicate samples for the rare earth elements (REEs) by inductively coupled plasma mass spectrometry (ICP-AAS) has been performed. Each finely ground sample (particle size <3 μm) was dispersed in 0.1% aqueous Triton X-100 solution and nebulized into an inductively coupled plasma. The resulting ions were detected by mass spectrometry. Parameters such as particle size, slurry concentration and argon carrier flow rate exercised a great influence on sensitivity, precision and accuracy of slurry nebulization/lCP-MS. Calibration curves were constructed using aqueous standard solutions. The extended dynamic range (EDR) detection system allowed the use of matrix element as an internal standard; this procedure was effective to correct the differences in sensitivity between the solution and the slurry methods. The optimum procedure was applied to the determination of REEs in standard silicate rocks of the Geological Survey of Japan. The precision ranged from 0.8 to 6.3 (RSD, %) for REEs contents of 0.13 - 38 ppm. Detection limits of REEs were excellent (0.002 - 0.02 ppm at the effective integrating time of 10 s).

Analysis of advanced ceramics and their basic products

A review on the analysis of the most important ceramic materials and their basic substances is given. The importance of minor and trace elements in the bulk as well as their distribution on the microscale in both classes of substances is discussed by the example of Al2O3, AlN, TiO2, Si3N4, SiO2, SiC, Y2O3, ZrO2-based and some other ceramics and of their basic substances. The state-of-the-art and trends of development in modern atomic spectrometric methods for bulk analysis of the basic substances subsequent to sample dissolution, such as plasma emission and mass spectrometry, but also of direct methods such as slurry nebulization for plasma spectrometry, inorganic mass spectrometry and X-ray spectrometry are discussed. Further, first approaches for the in-depth analysis of powders and trends in direct methods for compact ceramics based on laser evaporation as well as on electron and ion probe techniques are presented. The latter are illustrated with selected examples from the literature.

Slurry nebulisation of geological materials into argon, argon-nitrogen and argon-oxygen inductively coupled plasmas

The variation of net signal to background (S/B) ratios with observation height in Ar, Ar-N2 and Ar-O2, inductively coupled plasmas were studied for aqueous solutions and for slurries of homogeneous glasses. Trassy-Mermet demountable and extended torches were used. Whereas the S/B profiles for aqueous solutions varied smoothly, slurry atomisation produced irregular profiles attributed to differences in decomposition and atomisation of refractory particles and particles of varying grain size. The use of mixed gas plasmas for slurry atomisation results in a lowering of the zone of maximum S/B ratio and enhanced signals for some of the analyte lines. Differences were observed in the intensity profiles for both atom and ion lines and for the two torches used.

Feasibility of solid sample introduction by slurry nebulisation for inductively coupled plasma mass spectrometry

Three certified reference material soils and three industrial catalysts (mixed oxide, zeolite and chromium oxide) have been analysed by slurry nebulisation-ICP-MS and the results compared with those obtained by slurry nebulisation-ICP-AES and conventional procedures. The finely ground samples (particle size <3 µm) were dispersed in tetrasodium pyrophosphate solution and aspirated using a Babington-type nebuliser. Slurry concentrations of 0.05 g per 100 ml were used for the ICP-MS work and no cone blocking effects were observed. Calibration was with simple aqueous standards. Agreement between values obtained by slurry nebulisation and other techniques, or certificate values, was good for all elements (11) studied except Al. For Al, slurry nebulisation-ICP-MS results were ca. 10% low. The very high sensitivity of slurry nebulisation-ICP-MS was demonstrated by the semi-quantitative analysis of rare earth elements in soils. Clearly the method has considerable potential.