Jiang Zucheng

Recovery of Ce(IV) and Th(IV) from rare earths(III) with Cyanex 923

Solvent extraction of Ce(IV), Th(IV) with Cyanex 923 in n-hexane from sulphuric acid medium was studied with the dependence of the extraction on acidity and temperature being investigated. The Ce(IV) and Th(IV) extraction mechanism was proposed by slope analysis and the IR spectra of purified Cyanex 923 saturated with Ce(IV) were employed to determine the composition of the Ce(IV) complex. The equilibrium constant and thermodynamic functions of Th(IV) extraction were calculated and the characteristics of the stripping of Ce(IV), Th(IV) from the loaded organic phase were studied

Volatilization studies of lanthanum, yttrium and europium as their 1-phenyl-3-methyl-4-benzoylpyrazolone [5] complexes from an electrothermal vaporizer for sample introduction in inductively coupled plasma atomic emission spectrometry

A method for the determination of trace amounts of La, Y and Eu, based on the formation of volatile chelates between rare earth elements and 1-phenyl-3-methyl-4-benzoyl-pyrazolone [5] (PMBP) in a graphite furnace, is described. PMBP was used as a chemical modifier for the volatilization of La, Y and Eu from the electrothermal vaporizer into the ICP. The factors affecting the chelating reaction between La, Y and Eu and PMBP were studied in detail, and the vaporization behavior of the chelates formed in the graphite furnace was also investigated. It was found that the presence of an excess of PMBP was necessary to prevent the thermal decomposition of the chelates during the volatilization and transportation processes. Under the optimized conditions, the limits of detection for La, Y and Eu are 8.0, 1.0 and 0.9 ng ml–1, respectively, and the relative standard deviations range from 3.3% (La) to 4.0% (Y). The linear ranges of the calibration graphs span three orders of magnitude. The method was applied to the analysis of an environmental reference material and the results obtained were in good agreement with the reference values.

Slurry sample introduction with fluorinating electrothermal vaporization for the direct ICP-AES determination of boron in plant leaves

The slurry sample introduction with fluorinating electrothermal vaporization has been applied to ICP-AES for the determination of boron in plant leaves. The main working parameters for ETV-ICP-AES, such as r.f. power, gas flow rate, drying temperature and atomization temperature have been studied. The concentration of the fluorinating agent polytetrafluoro-ethylene was examined for the boron determination. The matrix concentrations of Na, K, Ca and Mg up to 5 mg/ml do not interfere with the fluorinating vaporization of boron. Several plant samples were analysed with the standard addition method. A good agreement of analytical results between this method and a spectrophotometric method was obtained. The determined value of boron in NBS SRM 1573 tomato leaves coincides with literature values.SummaryThe slurry sample introduction with fluorinating electrothermal vaporization has been applied to ICP-AES for the determination of boron in plant leaves. The main working parameters for ETV-ICP-AES, such as r.f. power, gas flow rate, drying temperature and atomization temperature have been studied. The concentration of the fluorinating agent polytetrafluoro-ethylene was examined for the boron determination. The matrix concentrations of Na, K, Ca and Mg up to 5 mg/ml do not interfere with the fluorinating vaporization of boron. Several plant samples were analysed with the standard addition method. A good agreement of analytical results between this method and a spectrophotometric method was obtained. The determined value of boron in NBS SRM 1573 tomato leaves coincides with literature values.

Slurry sampling of silicon nitride powder combined with fluorination assisted electrothermal vaporization for direct determination of titanium, yttrium and aluminum by ICP-AES

The vaporization behavior of silicon and three refractory trace elements (Al, Ti and Y) were studied in the presence and absence of a PTFE emulsion as fluorinating reagent and applying an electrothermal ICP-AES coupled system. It was found that during a 60 s ashing step at 700 °C about 90% of 100 µg of Si 3 N 4 can be decomposed and evaporated without considerable losses of the trace elements investigated. Calibration could be carried out by the standard addition method and the calibration curve method applying spiked slurries and aqueous standard solutions with peak height intensity measurements, respectively. The detection limits varied from 0.11 µg g –1 (Al) to 0.09 µg g –1 (Ti) with RSD 1.9-4.2%.

Slurry sampling and fluorination–electrothermal vaporization inductively coupled plasma atomic emission spectrometry for the direct determination of molybdenum in food

A method for the direct determination of Mo in various types of food by fluorination–electrothermal vaporization inductively coupled plasma atomic emission spectrometry has been developed and optimized. Slurry samples were prepared by ultrasonic wave vibration, after pre-treatment and direct injection into the graphite furnace using polytetrafluoroethylene as a fluorinating agent. The procedure was applied to the determination of Mo in National Institute of Standards and Technology Standard Reference Materials 1567 Wheat Flour, 1568 Rice Flour and 1577 Bovine Liver. The values found were in reasonable agreement with the certified values, with a detection limit of 0.7 ng ml–1 and an RSD of 3.2%(n= 10) at a concentration of 0.1 µg ml–1. The proposed procedure has been applied successfully to the analysis of various types of food samples; the recovery ranged between 92 and 105%.

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

The chemical modification of polytetrafluoroethylene (PTFE) slurry in electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) and in electrothermal atomic absorption spectrometry (ETAAS) was investigated and compared systematically. For both cases, the graphite furnace can be used as a chemical reactor in which the fluorinating reagent PTFE can convert the oxides of analytes into their volatile fluorides at high temperature. However, different influences resulting from fluorination in ETV-ICP-AES and ETAAS were observed owing to different functions of the graphite furnace in the two techniques. The formation of fluoride enhanced the emission signals of the refractory elements Mo, Cr and Yb significantly in ETV-ICP-AES, but only improved the sensitivity of Cr in ETAAS. In both ETV-ICP-AES and ETAAS, the addition of PTFE increased the maximum ashing temperature of volatile analyte cadmium. Moreover, PTFE can obviously reduce or remove the matrix interference and particle size effects of solid samples; this advantage is a benefit in the analysis of complicated samples, especially for the direct analysis of solid samples.

Use of polytetrafluoroethylene slurry for silica matrix removal in ETAAS direct determination of trace cobalt and nickel in silicon dioxide powder

A novel method for the direct determination of trace Co and Ni in SiO 2 powder by slurry sampling ETAAS was developed. At high temperature of the graphite furnace, a PTFE slurry in HNO 3 was used as a fluorinating reagent to convert the silica matrix into high-volatility fluoride, which was subsequently evaporated by selective vaporization prior to the atomization of analytes. In this case, the severe interference of the matrix on the vaporization and atomization of analytes was reduced significantly, and chemical attack of the excess of silica matrix on the graphite tube was also minimized. The proposed method was successfully applied to the determination of trace Co and Ni in SiO 2 powder with aqueous calibration and minimum chemical pre-treatment. For the direct analysis of high purity SiO 2 powder, the detect limits of Co and Ni were 18.8 and 35.0 ng g –1 , respectively. The analysis of NIES CRM2 Pond Sediment confirmed the reliability of the approach.

Determination of trace amounts of molybdenum in water samples by inductively coupled plasma atomic emission spectrometry after cobalt-dithiocarbamate coprecipitation

SummaryA method for the determination of trace amounts of molybdenum in fresh water and seawater samples by sequential ICP-AES with microsampling technique after cobalt-dithiocarbamate coprecipitation was developed. The precipitate was dissolved in 100 μl of diluted nitric acid (1:2), and the solution obtained was then introduced into an ICP via a concentric nebulizer. By use of 1.7 ml sample, a preconcentration factor of 17 was achieved. Different factors including integration time, sample volume, pumping rate as well as coprecipitation conditions such as pH of the solution, amounts of reagents, standing time for the precipitate and matrix effects were examined and optimized in detail. Under selected conditions the detection limit of the method for Mo is 0.52 μg/l using 1.7 ml sample. The procedure was applied to the analysis of water samples (artificial water and open ocean seawater reference material) with quantitative recovery. The analytical results were in good agreement with the certified value. The method is sensitive, simple, accurate and effective, also in the presence of interfering salts and can be applied to small sample volumes.

Direct determination of aluminium in biological materials by electrothermal vaporization-inductively coupled plasma atomic emission spectrometry with polytetrafluoroethylene as chemical modifier

Abstract A method for the determination of aluminium in biological materials with electrothermal vaporization and inductively coupled plasma atomic emission spectrometry is described, in which polytetrafluoroethylene (PTFE) is used as chemical modifier to improve the vaporization of aluminium. The absolute detection limit of aluminium is 5.0 pg and the R.S.D. is 2.2% at an aluminium concentration of 0.2 μg ml−1 (n = 9). The reliability of the entire procedure was confirmed by analyses performed on three standard reference biological materials.

Study of the determination of trace amounts of chromium by electrothermal atomic absorption spectrometry with a poly(tetrafluoroethylene) slurry as a chemical modifier

Using poly(tetrafluoroethylene) (PTFE) slurry as a chemical modifier, the process of vaporization and atomization of Cr in a graphite furnace for electrothermal atomic absorption spectrometry was investigated. It was shown that PTFE could react with Cr to form chromium fluoride and suppressed the formation of refractory metal carbides. The addition of PTFE clearly enhanced the analytical sensitivity of Cr and significantly reduced the interferences of a 103–104-fold excess of matrix elements. The detection limit (DL) and characteristic mass (mch) of the conventional method are 9.6 and 24.5 pg (Cr), respectively, whereas with PTFE the best DL and mch values of the proposed method are 2.73 and 10.0 pg (Cr), respectively. The calibration graph is linear in the range 5–80 ng ml–1 (Cr) with RSDs of 1.1–6.6%. The method was applied to the determination of trace amounts of Cr in surface water and copper chloride samples. The Cr recoveries from the samples were 96.4–103.7%.