Slurry Sampling Technique Research Articles

Green direct ultrasonic slurry sampling and electrothermal atomic absorption spectrometry method for metal analysis of solid plastics samples.

This work presents a "green" analytical method developed for the determination of potentially toxic metals such as aluminium, barium and chromium in solid plastics samples using the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry. The development of the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry entailed optimisation of the measuring conditions, which included optimisation of the temperature programme, selection of an appropriate liquid medium for slurry preparation, optimisation of the concentration and volume of the liquid medium and optimisation of the mass of the solid plastics sample. The following conditions were determined: the optimal pyrolysis temperature for aluminium, barium and chromium was in the range of 1300 °C to 1700 °C and the optimal atomisation temperature was in the range of 2100 °C to 2400 °C. The optimal liquid media for solid plastics samples were H2O, 0.2% (v/v) HNO3 and 0.2% (v/v) HCl. The optimal volume of liquid medium was in the range from 5 to 15 mL and the mass of the solid plastics samples was in the range from 30 to 100 mg. The limit of detection and limit of quantification were estimated as 0.06-0.52 ng g-1 and 0.22-1.69 ng g-1 for aluminium, 0.11-0.94 ng g-1 and 0.37-3.14 ng g-1 for barium and 0.07-0.31 ng g-1 and 0.25-1.04 ng g-1 for chromium. Relative standard deviation was below 5% for all plastic samples analysed. Based on the established validation parameters, the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry represents a viable technique for metal analysis of a variety of plastic materials. The concentrations of analytes in individual solid plastic samples were in the range of 1.36 ± 0.06 μg g-1 to 22.65 ± 0.66 μg g-1 for aluminium, 1.13 ± 0.03 μg g-1 to 6.01 ± 0.22 μg g-1 for barium and 0.60 ± 0.03 μg g-1 to 10.48 ± 0.46 μg g-1 for chromium.

Development of sensitive determination method for platinum in geological materials by carbon slurry sampling graphite furnace atomic absorption spectrometry

A simple and cost effective preconcentration method based on modified activated carbon is proposed for the determination of traces of platinum (Pt) in geological samples by the carbon slurry sampling technique for graphite furnace atomic absorption spectrometry (GFAAS). The basic parameters affecting the adsorption capacity of Pt(IV) ions on modified activated carbon were studied and the effect of activated carbon modification has been determined by studying the initial runs of adsorption isotherms. The influence of chlorides and nitrates on adsorption ability of Pt(IV) ions onto the modified activated carbon for diluted aqueous solution was also studied in detail in respect to the determination of platinum in solid materials following digestion steps as outlined in the analytical procedure, which usually involves the application of aqua regia. The XPS studies confirmed that not only the surface reduction of Pt(IV) ions into Pt(II) is the main platinum adsorption mechanism on the activated carbon. Determination of platinum after its preconcentration on the modified activated carbon was tested and validated by applying certified reference materials. The proposed method has been successfully applied for the determination of Pt in real samples using the standard calibration method.

Direct determination of fluorine in niobium oxide using slurry sampling electrothermal high-resolution continuum source molecular absorption spectrometry

Aiming for a round-robin test, a new method for the direct determination of fluorine in niobium oxide has been developed. It is based on the use of high-resolution molecular absorption spectra of calcium mono-fluoride (CaF) generated in the graphite tube, combined with the slurry sampling technique. The absorption measurement was performed at the 606.44nm CaF rotational line. By using graphite tubes with zirconium carbide (ZrC) modified platform, the molecular absorption sensitivity of CaF has been improved by a factor of 20, and no additional chemical modifier was necessary. Generally, non-spectral interferences were observed in the presence of HCl, H2SO4, and H3PO4. For HCl, additional spectral interference occurred due to an overlap of the absorption spectra of CaF and CaCl. However, due to the absence of these mentioned substances in the current material, such interferences do not exist for this application. The characteristic mass found for the CaF 606.44nm line was 0.1ng; the limit of detection was 5mg fluorine per kg solid sample (3σ criterion). The results obtained by the method were within the range of certified values. Comparing to the classical method such as the pyrohydrolysis-photometric method, the developed new method showed clear advantages regarding sensitivity and specificity. The time requirement for one sample analysis was strongly shortened from several hours to only some minutes.

Determination of macro and trace elements in multivitamin dietary supplements by high-resolution continuum source graphite furnace atomic absorption spectrometry with slurry sampling

In this research, three different commercially available multivitamin dietary supplements were analyzed by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) with slurry sampling. The concentrations of Cr, Cu, Fe, Mn, and Se were determined and compared to the amounts stated by producers. The safety of multivitamin dietary supplements depends on various factors including the manufacturing process and the purity and origins of the raw ingredients. For this reason, this research determined concentrations of several toxic elements (As, Cd, and Pb). Microwave-assisted high pressure Teflon bomb digestion was used to determine total amounts of elements in samples. Samples were prepared as slurries at a concentration of 0.1% (m/v) for macro elements (Cr, Cu, Fe, Mn, and Se) and at a concentration of % (m/v) for trace elements (As, Cd, and Pb) in acidic media (3M HNO3). The influence of acid concentration, Triton X-100 addition, sonication time, and sonication power on absorbance was investigated. The accuracy of this method was validated by analyses of NRCC LUTS-1 (Lobster hepatopancreas), NRCC DORM-1 (Dogfish Muscle), NRCC DOLT-2 (Dogfish Liver), NBS SRM 1570 (Spinach Leaves) and NBS SRM 1573 (Tomato Leaves) certified reference materials. The measured elements contents in these reference materials (except NRCC DOLT-2) were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level.

Preparation and evaluation of Ni-loaded activated carbon for enrichment of arsenic for analytical and environmental purposes

A new adsorbent based on thermal modification of activated carbon impregnated by nickel(II) nitrate was prepared and utilized for arsenic enrichment from aqueous solution. Various ratios of the impregnating agent to carbon mass were analyzed for the evaluation of arsenic adsorption capacity and selectivity. The properties of As(V) ions affecting the adsorption process on the prepared activated carbon were studied. The carbon impregnated with 10% Ni(NO3)2 and thermally treated at 250°C exhibited the highest adsorption capacity and selectivity towards arsenic ions. The physical and chemical properties of the Ni-loaded activated carbon were investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). These studies confirmed that the surface reactions of nickel oxides or hydroxides with arsenate ions enhanced the arsenic adsorption on the Ni-loaded activated carbon. Enrichment of arsenic from environmental samples onto the studied adsorbent was tested and successfully applied for As determination using the carbon slurry sampling technique for graphite furnace atomic absorption spectrometry determination (GFAAS) using the standard calibration method.

Trace Cd, Co, and Pb elements distribution during Sulcis coal pyrolysis: GFAAS determination with slurry sampling technique

A simple and fast method based on graphite furnace atomic absorption spectrometry (GF AAS) and slurry sampling technique (SlS) was developed to determine trace Cd, Co and Pb in high-sulphur coal (Sulcis, Italy) and coal chars derived at 600, 750 and 950°C under N2 atmosphere for developing a clean coal for electricity production. The proposed method was then coupled to a four-step sequential chemical extraction method for assessment of metals distribution in coaled samples. The slurries were prepared by varying sample mass (1–50mg), volume (1–3mL) and kind of dispersing medium (1% v/v Triton X-100 and 2N HNO3), and sonication time (5–30min). Pyrolysis/atomization temperatures as well carrier gas flow rate were optimised. Pd(NO3)2 and NH4H2PO4 were employed to stabilize Cd and Pb, respectively, in the pyrolysis stage of furnace program. The use of HNO3 as dispersing agent was found to be effective in lowering the high level of background absorption on the Cd analytical signal produced by raw coal matrix. Conversely, coal charred samples did not show significantly level of background interferences, so that Triton X-100 dispersing agent could be used for all analytes. Calibration curve against acid-matched standards was allowed for Cd, whereas the standard addition calibration was used for Co and Pb owing to chemical matrix interferences. The precision, expressed as relative standard deviation (% RSD, n=5), was better than 5% for Cd, Co, and Pb at 1, 10, and 15μgL−1 levels, respectively. The accuracy of the analytical method was checked by analyzing a BCR No. 182 steam coal certificated reference material and the results were in good agreement with certificated and informed values. The solid detection limits (3σblank) were as low as 0.001 Cd, 0.01 Co, and 0.01 Pb mgkg−1, using 30mg sample mass and slurry concentration of 30m v−1 for Cd, and 50mg sample mass and 50m v−1 slurry concentration for Co and Pb. The content of elements in Sulcis coal was found to be 0.33 Cd, 4.0 Co, and 3.8 Pb mgkg−1 and mostly associated to sulphates and di-sulphides as indicated by the leaching test. Under pyrolysis conditions Cd significantly volatilised (about 64%) at temperature higher than 600°C, whereas residue chars at 950°C are enriched in Co and Pb up to 20%. The proposed method is suitable for routine metals monitoring in coaled samples.

Alternative Solid Sample Pretreatment Methods in Green Analytical Atomic Spectrometry

ABSTRACT A review of recent literature utilizing alternative sample pretreatment methods for solid environmental and biological materials analysis to assess total metals content by atomic spectrometry is provided. All the selected treatments coincide with all or some of the fundamentals of Green Chemistry policy such as prevention of waste generation; safer and less toxic solvents and reagents; and designs for energy efficiency. The review covers the classic slurry sampling technique, mainly, its current trends, as well as developments based on the use of diluted acids, chelating agents solutions, or even water for leaching (extraction) methods assisted by ultrasounds, microwave energy, or pressurization. In addition, the use of conventional or assisted enzymatic hydrolysis procedures is also discussed.

Elemental analysis of flour-based ready-oven foods by slurry sampling inductively coupled plasma optical emission spectrometry

A slurry sampling technique has been utilised for the determination of Na, K, Ca, Mg, S, P, Fe, Mn, Cu and Zn in wheat-flour and flour-based ready-oven foods using ICP-OES and a direct aqueous calibration technique. For 0.1% w/v suspension of flour in 0.1% w/v Triton X-100 and 6% v/v HNO 3, the procedural limits of detection (all in mg kg −1) for Na, K, Mg, Ca, P, S, Fe, Zn, Mn and Cu were 7.51, 61.1, 0.645, 1.59, 5.25, 4.58, 1.50, 1.07, 0.867 and 1.58, respectively. The precision was expressed as the relative standard deviation (RSD) of 5–10% ( n = 10) for 0.1% w/v suspension of wheat-flour. The accuracy was confirmed by the analysis of reference materials wheat-flour GBW 08503 and rice flour NIST 1568a. The proposed method was applied to the analysis of two commercial samples of wheat-flour and four samples of flour-based ready-oven mixtures. The results have shown no significant differences when compared with those obtained after complete digestion of the samples analysed.

Chemometric investigation of systematic error in the analysis of biological materials by flame and electrothermal atomic absorption spectrometry

Systematic errors observed when using flame atomic absorption spectrometry (FAAS) and electrothermal atomic spectrometry (ETAAS) for the analysis of biological solid materials (seafood products) were evaluated. The effect of the sample pre-treatment method (microwave-assisted acid digestion, ultrasound-assisted acid leaching and slurry sampling) as well as the number of times that a certain pre-treatment process is repeated, were two factors evaluated. They give information about the effect of the sample pre-treatment on the uncertainty in the analysis. In addition, the number of measurements (i.e., number of times that an acid digest, an acid leachate or aqueous slurry are analysed) and the calibration technique used (aqueous calibration method or standard addition technique) were other two variables taken into account. This last factor gives information about the effect of the calibration on the results, while the replicate measurements showed the repeatability. A fifth variable named as sample matrix tests the influence of the matrix sample on the systematic error through the use of different reference materials. This variable allows the study of the effect of the trace element concentrations on the uncertainty because the trace elements contents are different in each reference material. Experimental design and principal component analysis approaches were used as chemometric tools. It has been found that the use of the slurry sampling technique in ETAAS and FAAS and the determination of high element concentrations by ETAAS have led to poor precision.

Determination of macro and trace element in multivitamins preparations by inductively coupled plasma optical emission spectrometry with slurry sample introduction

A slurry sampling technique has been utilised for elemental analysis of multivitamins preparations using inductively coupled plasma-emission spectrometry (ICP-OES). For results comparison, samples were mineralised. Slurry concentration 0.1–0.2% m/v in 6% v/v HNO 3, was used. The calibration by water standard solutions, slurry standards and standard additions were tested for determination above-mentioned elements in slurries. The method offers good precision for macro elements (RSD ranged from 5% to 10%). For in-home control sample, the measured concentrations are in satisfactory agreement with independent laboratories. For the analysed multivitamin preparations, the found element concentration is compared to amount declared by producer. The concentrations of Ca, Mg, P, K, Fe, Mn, Zn, Cu and Cr, Ni, V were determined in the range 1000–100,000 and 5–50 μg g −1, respectively. The slurry ICP-OES analysis was found to be suitable for quality control monitoring of multivitamin preparations and could be useful as a routine procedure.

Impaction collection and slurry sampling for the determination of arsenic, cadmium, and lead in sidestream cigarette smoke by inductively coupled plasma-mass spectrometry

The slurry sampling technique has been applied for the determination of arsenic, cadmium and lead in sidestream cigarette smoke condensate (SS CSC) by inductively coupled plasma mass spectrometry (ICP-MS). The smoke collection system consists of a "fishtail" chimney in conjunction with an impaction trap and a mixed cellulose ester (MCE) backup filter for the SS CSC collection. The smoke condensates, collected at three different regions of the system (i.e. the inner wall of the chimney, the impaction trap and the MCE filter), were individually prepared and analyzed and showed that about 70 and 20% of Cd and Pb, respectively, were trapped by the impaction trap and the MCE filter with less than 5% trapped by the chimney. In contrast, about 60% of As was trapped by the impactor and a relatively high percentage of As, about 30%, was deposited onto the inner wall of the chimney. The uneven distribution of trace metals at each collection stage strongly suggested that the composition of smoke aerosol and the associated physical form of the analytes may be different. The yields of As, Cd and Pb for the sidestream cigarette smoke of the 1R4F reference cigarette were 29.5 +/- 2.4, 421 +/- 6.6 and 46.4 +/- 0.9 ng cigarette(-1)(n= 3) respectively, when the cigarette was smoked according to the smoking regime: 45 mL puff volume of 2-s puff duration at an interval of 30 s with 50% ventilation holes covered. The analytical results for the slurry sampling technique were also compared with other sample preparation techniques and show good agreement.

Simultaneous determination of macro and trace elements in biological reference materials by microwave induced plasma optical emission spectrometry with slurry sample introduction

A slurry sampling technique (SST) has been utilized for simultaneous multi-element analysis by microwave-induced plasma optical emission spectrometry (MIP-OES). Slurry samples from a spray chamber are fed directly into the microwave cavity-torch assembly (power 300 W) with no desolvation apparatus. The performance of SST-MIP-OES was demonstrated by the determination of macro (Na, K, Ca, Mg, P) and trace (Cd, Cu, Mn, Sr, Zn) elements in three biological certified reference materials using a V-groove, clog-free Babington-type nebulizer. Slurry concentrations up to 1% m/v (particles <20 μm), prepared in 10% HNO 3 (pH 1.2) containing 0.01% of Triton X-100, were used with calibration by the standard additions method. The method offers relatively good precision (R.S.D. ranged from 7 to 11%) with measured concentrations being in satisfactory agreement with certified values for NRCC TORT-1 (Lobster hepatopancreas), NRCC LUTS-1 (Lobster hepatopancreas) and IAEA-153 (Milk powder). The concentrations of Na, K, Ca, Mg, P and Cd, Cu, Mn, Sr, Zn were determined in the range 90–22 000 μg/g and 1–420 μg/g, respectively. The method could be useful as a routine procedure.

Simultaneous direct determination of aluminum, calcium and iron in silicon carbide and silicon nitride powders by slurry-sampling graphite furnace AAS.

A fast and accurate analytical method was established for the simultaneous direct determination of aluminum, calcium and iron in silicon carbide and silicon nitride powders by graphite furnace atomic absorption spectrometry using a slurry sampling technique and a Hitachi Model Z-9000 atomic absorption spectrometer. The slurry samples were prepared by the ultrasonication of silicon carbide or silicon nitride powders with 0.1 M nitric acid. Calibration curves were prepared by using a mixed standard solution containing aluminum, calcium, iron and 0.1 M nitric acid. The analytical results of the proposed method for aluminum, calcium and iron in silicon carbide and silicon nitride reference materials were in good agreement with the reference values. The detection limits for aluminum, calcium and iron were 0.6 microg/g, 0.15 microg/g and 2.5 microg/g, respectively, in solid samples, when 200 mg of powdered samples were suspended in 20 ml of 0.1 M nitric acid and a 10 microl portion of the slurry sample was then measured. The relative standard deviation of the determination of aluminum, calcium and iron was 5 - 33%.

Electrothermal atomic absorption spectrometric determination of cadmium in bangladeshi vegetables with a metal tube atomizer and slurry sampling technique

Ultrasonic slurry sampling electrothermal atomic absorption spectrometry with a molybdenum tube atomizer has been applied for the determination of cadmium in vegetable samples in Bangladesh. The suspension-stabilizing medium was 10% glycerol solution. The optimum pyrolysis temperature was 300°C. The detection limit was 13 fg (3S/N). Matrix element interference was studied and it was found that thiourea as a chemical modifier eliminated the interference. The results for the determination of cadmium in vegetable samples by the proposed method were in good agreement with those measured in dissolved acid-digested samples. The method enables rapid calibration, and simple and rapid analysis of cadmium in vegetable samples at low cost.

Sample pre-treatment methods for the trace elements determination in seafood products by atomic absorption spectrometry

Different sample pre-treatments for seafood products have been compared with determine trace elements (As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se and Zn) by flame atomic absorption spectrometry (FAAS) and electrothermal atomic absorption spectrometry (ETAAS). Classic pre-treatments as microwave assisted-acid digestion and the slurry sampling technique were compared with new procedures such as microwave energy or ultrasound energy assisted-acid leaching process and enzymatic hydrolysis methodologies based on the use of pronase E. The methods were applied to DORM-1 and DOLT-1 reference materials with certified contents for the studied elements. The Student–Newman–Keuls (SNK) method was used to compare with element concentration means obtained with each sample pre-treatment and also the certified concentration means in both reference materials. Multivariate techniques such as principal components analysis (PCA) was also applied to comparative purposes.

Slurry sampling for the determination of arsenic, cadmium, and lead in mainstream cigarette smoke condensate by graphite furnace–atomic absorption spectrometry and inductively coupled plasma–mass spectrometry

The slurry sampling technique has been applied for the determination of As, Cd, and Pb in mainstream cigarette smoke condensate (MS CSC) by graphite furnace-atomic absorption spectrometry (GF-AAS) and inductively coupled plasma-mass spectrometry (ICP-MS). The MS CSC of the 1R4F Reference Cigarette was collected by electrostatic precipitation and was subsequently prepared as two slurry samples with and without the dispersing agent Triton X-100. Comparison of results determined by ICP-MS analyses of the 1R4F MS CSC slurry samples with those from the conventional microwave digestion method revealed good agreement. The precision of Triton X-100 slurry sampling and of microwave-assisted digestion was better than 10% RSD, and both were superior to slurry sampling without use of Triton X-100. The accuracy of the analytical results for the Triton X-100 slurry sample was further verified by graphite furnace-atomic absorption spectrometry (GF-AAS). For GF-AAS, the method limits of detection are 1.6, 0.04, and 0.5 microg x L(-1) for As, Cd, and Pb, respectively. For ICP-MS, the method limits of detection are 0.06, 0.01, and 0.38 microg x L(-1) for As, Cd, and Pb, respectively. The MS CSC of the 1R4F Reference Cigarette was collected in accordance with the Federal Trade Commission (FTC) smoking regime (35 mL puff volume of 2-s puff duration at an interval of 60 s) and the concentrations of As, Cd and Pb were 6.0+/-0.5, 69.3+/-2.8, and 42.0+/-2.1 ng/cigarette, respectively.

Application of multivariate methods to scalp hair metal data to distinguish between drug-free subjects and drug abusers

Human scalp hair samples of drug-free subjects and drug abusers (heroin and cocaine–heroin abusers) were analysed for trace metals by flame atomic absorption spectrometry (FAAS), flame atomic emission spectrometry (FAES) and electrothermal atomic absorption spectrometry (ETAAS). The classification of drug-free subjects and drug abuses groups with four multivariate methods using the metal contents in hair samples as discriminant variables has been discussed. Principal component analysis (PCA), cluster analysis (CA), linear discriminant analysis (LDA) and soft independent modelling of class analogy (SIMCA) allow distinguishing the two groups correctly. However, predictions by SIMCA are less satisfactory. Thirteen elements (Ag, Al, Ca, Cd, Cr, Cu, K, Mg, Mn, Na, Ni, Pb, and Zn) were determined by FAAS/FAES/ETAAS in 53 hair samples (16 samples of drug-free people and 37 samples of drug abusers). Human hair samples were prepared as aqueous slurries as sample pre-treatment and they were analysed using the slurry sampling technique. The half-range central value transformation was novelty used as data pre-treatment to homogenise the data. Grouping in the samples (drug-free people and drug abusers) were observed by using PCA and CA (squared Euclidean distance between objects and Ward method as clustering procedure). The application of LDA gave a correct recognition assignation percentage of 91.7 and 100.0% for the drug-free people and drug abusers, respectively, at a significance of 5%, while SIMCA offered recognition percentages of 83.3 and 91.3% for drug-free people and drug abusers, respectively, also at 5%. Finally, some studies were developed to classify heroin abusers and polidrug abusers (cocaine–heroin abusers) by the cited multivariate statistical methods. Recognition percentages of 90.9 and 100.0% were reached for heroin abusers and polidrug abusers groups, respectively, after LDA, while these percentages decreased to percentages lower than 90.0% when SIMCA was applied.

Direct analysis of silicon carbide by fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry using a slurry sampling technique

Slurry sampling in combination with fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) was employed for the direct determination of trace impurities in silicon carbide ceramic powders. The vaporization behaviors of silicon and five trace elements (Al, Cr, Cu, Fe and V) were studied in the presence and absence of polytetrafluoroethylene (PTFE) as fluorinating reagent. It was found that, during a 60 s ashing step at 800 °C, about 97% of 100 μg of SiC can be decomposed and evaporated without considerable losses of the trace elements investigated. Calibration was performed using the standard addition method and the calibration curve method, applying spiked slurries and aqueous standard solutions, respectively. The accuracy was checked by comparison of the results with those obtained by solution fluorination assisted ETV-ICP-AES and pneumatic nebulization (PN)-ICP-AES involving wet chemical decomposition of the sample. Detection limits between 0.3 μg g−1 (Al) and 0.08 μg g−1 (Cu) were achieved. The precision, expressed as the relative standard deviation (RSD), was between 6.0% (for 18.2 μg g−1 of Cr) and 2.8% (for 177 μg g−1 of Fe).

Rapid acid leaching and slurry sampling procedures for the determination of methyl-mercury and total mercury in human hair by electrothermal atomic absorption spectrometry

The use of the slurry sampling technique was applied for the determination of total mercury in human hair by electrothermal atomic absorption spectrometry (ETAAS). In addition, an acid leaching procedure with hydrochloric acid was developed in order to determine Me–Hg + in human hair with ETAAS. Palladium reduced by ascorbic acid was found to be adequate as a chemical modifier for both total mercury determination in hair slurries and methyl-mercury determination in hydrochloric acid solutions, at concentrations of 20 and 50 mg l −1 for palladium and ascorbic acid, respectively. The acid leaching procedure was carried out by mechanical stirring with hydrochloric acid at 4%, and a leaching time of 2 min was selected. The limits of detection were 0.04 and 0.10 μg g −1 for methyl-mercury and total mercury determination, respectively. The within-batch precision was between 1.8 and 8.8% for total mercury determination, and between 1.5 and 6.5% for methyl-mercury. The method was applied to 20 human hair samples from healthy people, and it was also applied to the CRM 397 human hair reference material, finding results that agree with the certified ones.

Direct determination of trace copper and chromium in silicon nitride by fluorinating electrothermal vaporization inductively coupled plasma atomic emission spectrometry with the slurry sampling technique

A method has been developed for the determination of trace impurities in silicon nitride (Si3N4) powders by fluorination assisted electrothermal vaporization (ETV) /ICP-AES using the slurry sampling technique. Polytetrafluoroethylene (PTFE) emulsion as a fluorinating reagent not only effectively destroys the skeleton of Si3N4, but also carries out selective volatilization between the impurity elements (Cu, Cr) and the matrix (Si). The experimental parameters influencing fluorination reactions were optimized. The detection limits for Cu and Cr are 1.05 ng/mL ( Cu) and 1.58 ng/mL (Cr), the RSDs are in the range of 1.9–4.2%. The proposed method has been applied to the determination of Cu and Cr in Si3N4 ceramic powders. The analytical results were compared with those obtained by independent methods.