Lifeng Zhong

Determination of rhenium content in molybdenite by ICP-MS after separation of the major matrix by solvent extraction with N-benzoyl-N-phenylhydroxalamine.

A simple and rapid analytical method for determining the concentration of rhenium in molybdenite for Re-Os dating was developed. The method used isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS) after the removal of major matrix elements (e.g., Mo, Fe, and W) from Re by solvent extraction with N-benzoyl-N-phenylhydroxylamine (BPHA) in chloroform solution. The effect on extraction efficiency of parameters such as pH (HCl concentration), BPHA concentration, and extraction time were also assessed. Under the optimal experimental conditions, the validity of the separation method was accessed by measuring (187)Re/(185)Re values for a molybdenite reference material (JDC). The obtained values were in good agreement with previously measured values of the Re standard. The proposed method was applied to replicate Re-Os dating of JDC and seven samples of molybdenite from the Yuanzhuding large Cu-Mo porphyry deposit. The results demonstrate good precision and accuracy for the proposed method. The advantages of the method (i.e., simplicity, efficiency, short analysis time, and low cost) make it suitable for routine analysis.

Mercury profiles in surface sediments from ten bays along the coast of Southern China

Spatial and temporal variations of mercury (Hg) were investigated from ten representative bays along the coast of Southern China. The total Hg (THg) in surface sediments varied widely with concentrations from 25 to 264 ng/g. As a whole, Hg pollution in several bays occupied by busy sea traffic and industrial activities, such as Shantou (ST) Bay and Dapeng (DP) Bay were remarkably more serious than others, which reflected the direct effects of anthropogenic activities around the coastal areas. Hg variations in sediment cores clearly display upcore rising trend which obviously correlates with the trend of economic development and urbanization in the last five decades. No significant correlations were found between Hg and organic matter and particle size, suggesting that the distribution of Hg is not fully controlled by these variables.

A method for determination of PGE-Re concentrations and Os isotopic compositions in environmental materials

Automobile catalyst emissions not only result in increasing environmental concentrations of Pt, Pd, and Rh, but also Os, Ir, and Ru. Little is known about the behavior of platinum-group elements (PGE) and Re in the environment and their potential risk to humans and, as such, the monitoring of Os, Ir, Ru, and Re concentrations in environmental samples is necessary. We present an improved procedure for determination of PGE-Re concentrations and Os-187/Os-188 ratios of the environmental reference material BCR-723 by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) and negative thermal ionization mass spectrometry (N-TIMS), respectively. The sample is digested with inverse aqua regia in a Carius tube. After Os separation by CCl4 solvent extraction, separation and purification of PGE and Re from sample matrix elements is sequentially performed by a two-stage tandem column setup using cation exchange and N-benzoyl-N-phenylhydroxylamine (BPHA) extraction resin. Elution of 0.1 mol L-1 HCl efficiently removes interfering elements such as Zr, Hf, Mo, and Cd in the final purified sample prior to ID-ICP-MS determination of PGE and Re. Analyses of BCR-723 yield reproducible results and well-defined average Pt, Pd, Os, Ir, Ru, and Re concentrations of 79.8 +/- 6.0, 4.6 +/- 0.8, 0.37 +/- 0.04, 0.23 +/- 0.12, 1.1 +/- 0.3, and 6.5 +/- 0.1 ng g(-1), respectively (95% confidence level; n = 10). The Os-187/Os-188 ratio of this standard was determined to be 0.537 +/- 0.022 (95% confidence level; n = 10). These are the first comprehensive PGE and Re concentrations and Os isotopic compositions reported for BCR-723 and provide a well-characterized standard for assessing the data quality of autocatatyst PGE measurements and related research on environmental materials. The method was successfully employed in the determination of PGE and Re concentrations and Os isotopic compositions in urban road dust samples.