Abstract: The described system contained a Gilson eight-channel peristaltic liquid delivery pump and Viton and Tygon tubes for feeding the organic and aqueous solution, respectively, while the extraction and back-extraction, respectively, were performed in 1- and 2-m Teflon coils each with a segmentor at the inlet and a sandwich-type Teflon phase separator (Sanuki Kogyo Co. Ltd., Tokyo, Japan) at the outlet and Teflon connecting tubes. The rare-earth elements were extracted from the sample solution (2 mL min-1) into a 0.1 M solution of bis-(2-ethylhexyl) hydrogen phosphate - 2-ethylhexyl dihydrogen phosphate (13:7) in hexane (0.6 mL min-1). The ensuing separated organic phase was mixed with octyl alcohol - heptane (1:1; 0.6 mL min-1) and then back-extracted with aqueous 2 M HNO3 containing 50 ng mL-1 of Cd as internal standard (0.4 mL min-1). The separated aqueous phase was then analyzed in a VG PlasmaQuad instrument with a Jarrell - Ash nebulizer (conditions detailed). The method was applied to synthetic sea water samples (enrichment factor 10; detection limits ranging from 0.16 pg g-1 of Tb, Ho or Lu to 1.2 pg g-1 of Nd) and to JG1a and JB1 standard rock and Jilin chondrite rock samples giving results which agreed with those obtained previously (procedures detailed).

Abstract: An online column pre-concentration method is described for the determination of Re in seawater by inductively coupled plasma mass spectrometry. Minicolumns of 2 sizes (7 mm x 2 mm i.d. and 14 mm x 2 mm i.d.) containing the anion-exchange resin Dowex 1-X8 were used for the quant. pre-concentration of Re in seawater. The concentrated Re was eluted from the column with HNO3. A simple calibration technique with Lu as internal standard and also isotope dilution were used for the determination of Re in seawater. Enrichment factors of 38- or 101-fold were obtained using 10- or 50 mL seawater samples, respectively., and the relative standard deviations for replicate measurements (n = 3) were 2.62% for natural seawater and 0.34% for synthetic seawater. The detection limits after online pre-concentration of 10 and 50 mL of seawater were 0.27 and 0.1 pg/mL, respectively. Almost no contamination blank signal or matrix interferences were observed