Electrothermal Vaporization Inductively Coupled Plasma Atomic Emission Spectrometry Research Articles

On-line cloud point extraction combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry for the speciation of inorganic antimony in environmental and biological samples

A new method for the determination of inorganic Sb species by on-line cloud point extraction combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) is presented and evaluated. The method is based on the complexation of Sb(III) with pyrrolidine dithiocarbamate (PDC) which form an hydrophobic complex at pH 5.5 and subsequently enter surfactant-rich phase at pH 5.5, whereas Sb(V) remained in aqueous solutions. The preconcentration step is mediated by micelles of the non-ionic surfactant Triton X-114 with ammonium pyrrolidine dithiocarbamate (APDC). The micellar system containing the complex was loaded into the FIA manifold at a flow rate of 2.5 mL min −1, and the surfactant-rich phase was retained in a microcolumn packed with absorbent cotton, at pH 5.5. After the surfactant-rich phase was eluted with 100 μL acetonitrile, it was determined by ETV-ICP-AES. Sb(V) is reduced to Sb(III) by l-cysteine prior to determined total Sb, and its assay is based on subtracting Sb(III) from total antimony. The main factors affecting separation/preconcentration and the vaporization behavior of analyte in graphite tube were investigated in detail. Under the optimized conditions, the precision relative standard deviation (R.S.D.) for eight replicate measurements of 0.2 μg mL −1 Sb(III) was 4.3%. The apparent concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for ETV-ICP-AES detection and in the initial solution, was 872 for Sb(III). The limit of detection (LOD) for Sb(III) was 0.09 μg L −1. The proposed method was successfully applied for the speciation of inorganic antimony in different water samples and urine sample with satisfactory results.

Application of low temperature electrothermal vaporization ICP-AES for determination of refractory yttrium with 1-(2-pyridylazo)-2-naphthol as chemical modifier

A low temperature electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) method was developed for the determination of the refractory yttrium, using 1-(2-pyridylazo)-2-naphthol (PAN) as chemical modifier. The trace yttrium was vaporized as PAN complex into plasma from a graphite furnace at a comparatively low temperature of 1200 °C. The operation conditions were optimized, and the vaporization behavior of Y–PAN chelate and the main factors affecting the determination were investigated in detail. Under the optimized conditions, the detection limit of Y was 0.7 ng ml −1, and the relative standard deviation (R.S.D.) for 0.1 μg ml −1 Y was 4.5% ( n=9, v=10 μl). The linear range of calibration curve covered three orders of magnitude. The recommended approach has been applied for analysis of three biological samples with satisfactory results. The accuracy of the method was demonstrated by analyzing two standard reference materials.

Slurry Sampling Electrothermal Vaporization Combined with ICP-AES for Direct Analysis of Environmental Samples

In this article, a polytetrafluoroethylene (PTFE) slurry was used as a chemical modifier for direct determination of trace elements in environmental samples by electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) with slurry sampling. The vaporization behaviors of the analytes in slurry and solution were comparatively studied in the presence of PTFE. The main influence factors for this method were examined. Under the optimum operating conditions, the precision of this method was better than 7% with the detection limits varying from 1.7 ng mL−1 (Cu) to 203 ng mL−1 (Zn). The proposed method has been applied to the direct determination of the trace elements in camphor tree leaves and standard reference material (the combined sample of branch and leaf of shrub, GBW 07603) with satisfactory results.

Speciation of chromium(III) and chromium(VI) by in situ separation and sequential determination with electrothermal vaporization inductively coupled plasma atomic emission spectrometry

A novel method for the speciation of chromium(III) and chromium(VI) by in situ separation and sequential determination with electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) was developed. The reaction conditions between Cr(III) and 8-hydroxyquinoline (8-Ox) and the vaporization behavior of the chelate formed were investigated in detail. It was found that the Cr(III)-8-Ox chelate could be formed at room temperature and vaporized from graphite furnace under controlled experimental conditions, therefore, an in situ separation of Cr(III) from Cr(VI) was achieved. The retained Cr(VI) in graphite tube was then determined by using fluorination vaporization ETV-ICP-AES with PTFE slurry as chemical modifier. Under optimum experimental conditions, the detection limits for Cr(III) and Cr(VI) are 8.6 ng/ml and 11.3 ng/ml, and the relative standard deviations (R.S.D.s) are 3.8% and 4.1% ( c=0.1 μg/ml, n=6), respectively. The linear ranges of the calibration curve for both Cr(III) and Cr(VI) covered three orders of magnitude. The proposed method has been applied to the speciation of Cr(III) and Cr(VI) in water samples with the satisfactory results.

Low temperature vaporization for ICP-AES determination of palladium in geological samples using sample introduction of gaseous palladium oxinate

A low temperature electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) method for the determination of palladium, by using sample introduction of gaseous palladium oxinate, was developed. The thermally stable palladium oxinate was formed and vaporized at a temperature of 900 °C from the graphite furnace. The main factors affecting the vaporization behavior of the analyte were investigated in detail. The detection limit of palladium for this method was 50 pg, and the relative standard deviation (RSD) for 0.2 µg ml−1 palladium was 4.7% (n = 8). Compared with conventional ETV-ICP-AES, the analytical sensitivity of this method was improved by one order of magnitude. The proposed method was applied to the determination of trace palladium in geological samples with satisfactory results.

In-situ separation of chromium(III) and chromium(VI) and sequential ETV-ICP-AES determination using acetylacetone and PTFE as chemical modifiers.

Electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-ES) has been used for the sequential determination of Cr(III) and Cr(VI). The method is based on the difference between the chelate reactions of the two Cr species and acetylacetone. Cr(III) chelate was separated from Cr(VI) and determined with use of acetylacetone as chemical modifier. The retained Cr(VI) in graphite tube was analyzed subsequently, after addition of polytetrafluoroethylene (PTFE) as chemical modifier. The different factors affecting the vaporization behavior of Cr(III) acetylacetonate were investigated in detail. The detection limits for Cr (III) and Cr(VI) were 0.56 and 1.4 ng mL(-1), respectively, and relative standard deviations for 0.1 microg mL(-1) Cr(III) and 0.1 microg mL(-1) Cr(VI) were 2.5% (n = 6) and 4.8% (n = 6), respectively. The linear ranges of the calibration curve for both Cr(IIl) and Cr(VI) covered three orders of magnitude. The proposed method was used to analyze water samples with satisfactory results.

Slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry for the direct determination of metal impurities in aluminium oxide ceramic powders.

A new analytical procedure for the direct determination of metal impurities (Cr, Cu, Fe and V) in aluminium oxide ceramic powders by slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) is reported. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of impurity elements in aluminium oxide ceramic powders from the graphite tube. A vaporization stage with a long ramp time and a short hold time provided the possibility of temporal analyte-matrix separation. The experimental results indicated that a 10 microL 1% m/v slurry of aluminium oxide could be destroyed and vaporized completely with 600 micrograms PTFE under the selected conditions. Two aluminium oxide ceramic powder samples were used without any additional pretreatment. Analytical results obtained by using standard addition method with aqueous standard solution were checked by comparison of the results with pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition and analyte-matrix separation. The limits of detection (LODs) between 0.30 microgram g-1 (Fe) and 0.08 microgram g-1 (Cu) were achieved, and, the repeatability of measurements was mainly better than 10%.

Tungsten coil devices in atomic spectrometry: absorption, fluorescence, and emission.

In this work, tungsten coil (W-Coil) devices are used as atomizers for electrothermal atomization atomic absorption spectrometry (ETAAS), electrothermal atomization laser excited atomic fluorescence spectrometry (ETA-LEAFS), and electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES). For most cases in ETAAS and ETA-LEAFS, limits of detection (LODs) using the W-Coil are within a factor of ten of those observed with commercial graphite furnace systems. LOD for Cd by W-Coil AAS is 10 pg, while LODs for As, Se, Cr, Sb and Pb by W-Coil LEAFS are 950, 320, 1400, 330, and 160 fg, respectively. The compact W-Coil device makes it an ideal atomizer for portable atomic spectrometry instrumentation, especially when coupled with a miniature charge coupled device spectrometer. Alternatively, the atomizer can be used as an inexpensive, modular add-on to an existing commercial ICP-AES system; and the thermal separation of Pb with interference elements Al, Mn, and Fe is demonstrated.

Determination of Rare Earth Impurities in High-purity Lanthanum Oxide Using Electrothermal Vaporization/ICP-AES after HPLC Separation

A new method for determination of trace rare earth impurities in high-purity La2O3 by HPLC combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) is proposed. The chromatographic retention behaviors of matrix (La) and rare earth impurities were studied using 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (P507) resin as the stationary phase and dilute nitric acid as the mobile phase. It was found that the use of EDTA as an eluent enables effective elution of rare earth impurities from a HPLC column. The influence of EDTA in ETV-ICP-AES was also discussed. The experimental results showed that a favorable separation between matrix (La) and rare earth impurities could be obtained within 30 min. The method proposed has been applied to the analysis of high-purity La2O3; the results obtained were in good agreement with those obtained by ICP-MS. Under the optimum conditions, the detection limits (DLs) for 14 rare earth elements (REEs) were in the range of 0.8 ng/ml (Yb) to 48 ng/ml (Ce). The recoveries of 14 REEs were in the range of 90% to 110%.

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).

Determination of trace rare earth impurities in high-purity cerium oxide by using electrothermal vaporization ICP-AES after HPLC separation with 2-ethylhexyl hydrogen 2-ethylhexylphosphonate resin as the stationary phase

A method is proposed to determine trace rare earth impurities in high-purity CeO2 by HPLC combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES). The chromatographic retention behaviours of the matrix (Ce) and rare earth impurities were studied using 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (P507) resin as the stationary phase and dilute nitric acid as the mobile phase. It was found that the matrix (Ce) can be separated quantitatively with dilute nitric acid as the mobile phase, and the rare earth impurities (Pr–Lu) can be eluted effectively by use of EDTA as an eluent. The experimental results show that a favorable separation between the matrix (Ce) and rare earth impurities (Pr–Lu) can be obtained within 60 min. The method proposed has been applied to determine 14 rare earth impurities in high-purity CeO2 with satisfactory results.

Study on the direct analysis of solid powder biological samples using fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry with PTFE slurry modifier

A method has been described for the direct determination of Ti, Cu, Mn, Cr and Cd in solid biological samples without any chemical pretreatment by fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) with slurry sampling. A polytetrafluorethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of the analytes from the graphite furnace. The interface between furnace device and ICP torch and the main factors affecting the analytical signal were investigated systematically. The detection limits for the determination of Ti, Cu, Mn, Cr and Cd are 6.3, 4.7, 10, 13 and 278 ng/mL, respectively; the relative standard deviations are in the range of 1.5 (Mn) ∼4.0% (Cd) after optimization of the operating conditions. The recommended approach has been applied to directly determine the trace elements of interest in the Chinese traditional medicine Loulu and in the solid biological standard reference material (peach leaves, GBW 08501) with satisfactory results.

The application of chemical modification in electrothermal vaporization-inductively coupled plasma atomic emission spectrometry

In this paper, several fluoride chemical modifiers have been tested for electrothermal vaporization-inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) determination of different volatile elements, such as refractory element Ti, medium volatile element Ni and easy volatile element Pb. Reagents tested include polytetrafluoroethylene (PTFE), NH 4F, NaF and CuF 2·2H 2O. The best overall results are obtained using 6% PTFE added to sample. Under the compromise operating conditions, the detection limits of analytes are in the range of 0.8–59 ng ml −1 and the calibration curves are linear for over three orders of magnitude. The direct determination of Ti, Ni and Pb in GBW 08505 tea leaves reference sample is shown as an example of PTFE chemical modification.

Comparative studies on chemical modification of polytetrafluoroethylene slurry in ETV-ICP-AES and ETAAS

W. Fuyi, J. Zucheng, H. Bin and P. Tianyou, J. Anal. At. Spectrom., 1999, 14, 1619 DOI: 10.1039/A904639I

Separation/Preconcentration of Lanthanum and Europium by Micro-Column Packed with Immobilized 1-Phenyl-3-methyl-4-bonzoyl-5-pyrazone on Microcrystalline Naphthalene and Determination by Electrothermal Vaporization Inductively Coupled Plasma-Atomic Emission Spectrometry.

A sensitive and rapid method for electrothermal vaporization-inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) determination of La 3+ and Eu 3+ after separation/preconcentration by a micro-column packed with immobilized 1-phenyl-3-methyl-4-benzoyl-5-pyrazone (PMBP) on microcrystalline naphthalene has been developed. Various influencing factors, such as the acidity of the aqueous solution, flow rate, volume of the sample, dimension of the micro-column on the separation and the preconcentration of the analyte, have been studied, and the working parameters were optimized experimentally. The choice of the solvent for dissolving the concentrated material and the effects of diverse ions have also been discussed in detail. The detection limits for ETV-ICP-AES determinations of La and Eu with PMBP as a chemical modifier are 160 pg and 30 pg, respectively, under optimized experimental conditions. Relative standard deviations of 4.2% and 3.1% have been obtained after eight replicate determinations at the 10 ng/ml level for La and Eu, respectively. The La and Eu contents in the standard reference material of Vehicle Exhaust Particulates (NIES No.8) and Citrus Leaves (NIST SRM 1752) determined by the proposed method are in good agreement with the reference values.

Determination of Rare Earth Impurities in High Purity Zirconium Dioxide by Electrothermal Vaporization Inductively Coupled Plasma Atomic Emission Spectrometry Using 1-Phenyl-3-Methyl-4-Benzoyl-5-Pyrazone as Extractant and Chemical Modifier

ABSTRACT A novel method has been developed for the determination of trace La, Eu and Y in high purity ZrO2 by electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) with 1-phenyl-3-methyl-4-benzoyl-5-pyrazone (PMBP) as extractant and chemical modifier. The matrix was quantitatively separated from the selected elements in 6M HNO3 medium by extraction with 0.1M PMBP in chloroform. The vaporization behaviors, effect factors and analytical characteristics of above selected elements were investigated in detail. Under the optimized conditions, the detection limits were 8.0, 0.9 and 1.0ng ml−1 for La, Eu and Y with the relative standard deviations of 3.3, 3.4 and 4.0% (n=7, c=0.5 μg ml−1), respectively. The proposed method has been applied to determine trace impurities in ZrO2.

Solid sampling electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES): influence of some ICP operating param

Some parameters of solid sampling electrothermal vaporization inductively coupled plasma atomic emission spectrometry (SS-ETV-ICP-AES) were investigated. The study concentrates on the determination of Cu, Cd and Pb. Observation height and carrier gas flow rate were optimized for different materials. Observation heights were found to be only slightly influenced by the matrix, which however, has a large impact on the optimal carrier gas flow rate. Radio frequency (rf) power has little influence on the signal, but for a higher forward power, the plasma will tolerate a higher matrix loading. The transport relative efficiencies for pneumatic nebulization, liquid-ETV (solution-ETV) and solid sample ETV (SS-ETV) for different solid materials were compared. In the case of Cd, the transport efficiency for ETV-ICP-AES was found to be about 10–30 times higher than with pneumatic nebulization whereas for Cu only, a factor of 4 and for Pb a factor of 10 was observed. Between solution-ETV and SS-ETV no significant difference was found for the transport efficiencies of Cu and Pb for different matrices, while the efficiency of the Cd transport turned out to be highly matrix-dependent.

Use of the simplified generalized standard additions method for calibration in solid sampling electrothermal vaporization inductively coupled plasma atomic emission spectrometry

To find a useful calibration strategy for the direct analysis of solid samples by electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES), the simplified generalized standard additions method was investigated. This method leads, by varying both the mass of the solid sample and the amount of analyte (standard solution) added, to a response surface from which the analyte concentration can be deducted by multiple linear regression. The analytical results obtained for Cu, Pb and Cd determinations in a number of biological and environmental reference materials are in good agreement with the certified values. The number of data points required to yield precise results (typical RSD < 10%) depends on the sample homogeneity.

Fluorination and volatilization of refractory elements from a graphite furnace for sample introduction into an inductively coupled plasma by using a polytetrafluoroethylene slurry

A method was developed to determine refractory elements by inductively coupled plasma atomic emission spectrometry (ICP-AES) with sample introduction by electrothermal vaporization. A slurry of polytetrafluoroethylene was used to form fluorides rather than carbides of the elements. In this way, the refractory elements were efficiently vaporized and subsequently introduced into the plasma. The detection limits for Zr, V, Cr, W, Mo, B and Ti were improved by a factor of 7–119, compared with those of electrothermal vaporization ICP-AES without the fluorinating agent. No memory effects were observed and adequate precision was obtained. The fluorination process is also discussed.