Distributions of major-to-ultratrace elements among the particulate and dissolved fractions in natural water as studied by ICP-AES and ICP-MS after sequential fractionation.

In order to elucidate the distributions of the elements among the particulate and dissolved fractions in pond water, major-to-ultratrace elements in different sizes of particles as well as in the filtrate passed through the 0.05 microm filter were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The different sizes of particle samples (ca. 100-300 microg each) were collected on the membrane filters with pore sizes of 10, 3.0, 1.2, 0.4, 0.2 and 0.05 microm, respectively, by sequential fractionation. As a result, about 40 elements in different sizes of particles could be determined by ICP-AES and ICP-MS, after acid digestion using HNO3/HF/HClO4. Then, the fractional distribution factors of major-to-ultratrace elements among the particulate and dissolved fractions were estimated from the analytical results. The total contents of Al, Fe, Ti, REEs (rare earth elements), Bi, Pb and Ag in the particulate fractions (larger than 0.05 microm) were more than 80-90%, while those of Ca, Sr, Cs, W, Ba, Mn and Co in the dissolved fraction, which corresponded to the filtrate passed through the 0.05 microm membrane filter, were more than 80%. It was further found that the fractional distributions of Cu and Zn in the dissolved fraction were ca. 50%. In addition, the enrichment factors (EFs) of the elements in the particulate fractions with particle sizes of 3.0-10 microm and 0.05-0.2 microm were estimated to elucidate their geochemical characteristics in natural water.

Determination of heavy metals and rare earth elements in environmental samples by ICP-MS after solid phase preconcentration with chelating resin fibers and anion exchanger filters.

A solid phase collection/concentration method using anion exchanger filters and a small syringe packed with chelating resin fibers is adopted as a preconcentration tool for trace elements and a separation tool for matrices in aqueous samples prior to the measurement by inductively coupled plasma-mass spectrometry (ICP-MS). The effects of fiber volume, sample volume, eluent volume, and sample flow rate on metal recoveries were investigated in detail to obtain optimum pretreatment conditions. Several heavy metals (HMs) such as, V, Mn, Co, Ni, Cu, Zn, Ga, Cd, Pb, Th and U, as well as 14 rare earth elements (REEs) in sample solutions at pH 6 were quantitatively collected on the solid phase. These adsorbed elements were completely recovered by eluting with 2 ml of 1.0 M nitric acid. At pH 6, more than 99% of alkali and alkaline earth metals in sample solutions were eliminated. The proposed method was evaluated by analyzing two standard reference materials (SRM): peach leaves (NIST 1547) and pond sediment (NIES No. 2). The solid samples were decomposed by microwave-heating and pressurizing acid digestion technique, and then treated by the proposed syringe-type pretreatment method, followed by the ICP-MS measurement. The analytical results for HMs in the SRMs obtained by the present method agreed well with the certified values.

Partitionings and kinetic behaviors of major-to-ultratrace elements between industrial waste incineration fly and bottom ashes as studied by ICP-AES and ICP-MS.

The partitionings of major-to-ultratrace elements between industrial waste incineration fly ash (IWIFA) and industrial waste incineration bottom ash (IWIBA) in industrial waste incinerators were investigated by measuring their concentration distributions, where the incineration ash samples were collected from three different types of industrial waste incinerators. The concentrations of the elements in the incineration ash samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). As a result, ca. 40 elements in the concentration range from mg g(-1) to sub-microg g(-1) could be determined in both IWIFA and IWIBA samples. The concentration ratios of CF/CB (CF, concentration in fly ash; CB, concentration in bottom ash) for analyte elements were used to evaluate the partitionings of the elements between fly and bottom ashes. Then, the correlations between the CF/CB values of the elements and the dissociation energies of their monoxides were examined to evaluate the kinetic behaviors of the elements during the incineration processes. It was found that lithophile and siderophile elements, which have a large affinity with oxygen, were almost equally distributed between fly and bottom ashes, regardless of the dissociation energies of their monoxides. On the other hand, chalcophile elements with rather large volatility provided different behaviors; the elements with the smaller dissociation energies of monoxides were more partitioned in fly ashes than those with the larger ones.

Estimation of metal impurities in high-purity nitric acids used for metal analysis by inductively coupled plasma-mass spectrometry.

A simple method to estimate the amounts of ultra-trace metal impurities in nitric acid reagents has been developed. The determination of sixty-four metals in nitric acid was accomplished by direct measurements of 0.1 M nitric acids accurately diluted with ultrapure water by ICP-MS. Though accurate metal concentration could not be obtained for all of the elements, we could effectively evaluate the nitric acid quality by comparing the ion counts of the samples, ultrapure water and standard metal solutions for a calibration prepared with Ultrapur nitric acid.

Adsorption behavior of mercury and precious metals on cross-linked chitosan and the removal of ultratrace amounts of mercury in concentrated hydrochloric acid by a column treatment with cross-linked chitosan.

Cross-linked chitosan was synthesized with chitosan and ethylene glycol diglycidyl ether. The adsorption behavior of trace amounts of metal ions on the cross-linked chitosan was systematically examined by packing it in a mini-column, passing a metal solution through it and measuring metal ions in the effluent by ICP-MS. The cross-linked chitosan adsorbed mercury and precious metals (Pd, Pt, and Au) at pH values from acidic to neutral. Especially, mercury in concentrated hydrochloric acids could be adsorbed on cross-linked chitosan quantitatively by an anion-exchange mechanism in the form of a stable chloride complex. This method was applied to the removal of mercury from commercially available hydrochloric acid; more than 97% of mercury was removed, and the residual mercury in the hydrochloric acid (Grade: for trace analysis) was found to be 0.15 ppb. Mercury adsorbed on the cross-linked chitosan could be easily desorbed with an eluent containing I M hydrochloric acid and 0.05 M thiourea. The thus-refreshed cross-linked chitosan could be repeatedly used for the removal of mercury in hydrochloric acid.

Inductively coupled plasma mass spectrometric determination of heavy metals in sea-water samples after pre-treatment with a chelating resin disk by an on-line flow injection method.

A new on-line flow injection (FI) pre-treatment system using a disk-type chelating resin (5 mm diameter, 0.5 mm thickness) was developed for the simultaneous multi-element determination of trace metals in sea-water samples by inductively coupled plasma mass spectrometry (ICP-MS). A chelating resin possessing an iminodiacetate (IDA) functional group was used for the collection of trace elements and the elimination of alkali and alkaline earth metals in highly concentrated salt solution. A 1 ml volume of a sea-water sample (pH 5.5) was applied to the chelating resin disk. Considering the removal efficiency for Ca, 50 mM ammonium acetate buffer solution (pH 5.5) was chosen as a sample carrier. The enriched trace metals were eluted with 0.1 M nitric acid and the eluate flowed into the ICP-MS system. The processing time for one sample was < 6 min (350 s). One of the important observations is the possibility of working with a low recovery, even lower than 50%. For example, several elements such as Mn, Cr, As, Mo, Ba and U, the recovery of which was < 50% in a batch-wise method, showed good linearity and reproducibility. The proposed method was evaluated by analyzing two kinds of sea-water certified reference materials, CASS-4 and NASS-5. Analytical data for eight heavy metals, V, Mn, Co, Ni, Cu, Mo, Cd and U, obtained from the present study agreed well with the certified values.

Development of column-pretreatment chelating resins for matrix elimination/multi-element determination by inductively coupled plasma-mass spectrometry.

Chelating resins, two kinds of iminodiacetate derivatives (IDA) of cross-linked chitosan (CCS) were synthesized and investigated for adsorption capacity, matrix elimination and collection/concentration of analytes by a column pretreatment in a multi-element ICP-MS determination method. The adsorption behavior of 54 elements at the 10 ng ml(-1) level on chitosan derivatives in a packed mini-column was systematically examined. Almost 30 kinds of metal ions were recovered quantitatively at pH 5 with CCS-HP/IDA (cross-linked chitosan possessing N-2-hydroxypropyl iminodiacetic acid groups) column. Compared with available chitosan-iminodiacetate resin, CHITOPEARL CI-03, the recovery of the metal ions such as Cu, Pb and La is satisfactory with CCS-IDA (cross-linked chitosan possessing N,N-iminodiacetic acid groups) and CCS-HP/IDA using 2 M nitric acid as an eluent, which may be attributed to the difference of cross-linking and macroporous structure. Compared with Chelex-100, the adsorption efficiency is in the order: Chelex-100 > CCS-IDA > CCS-HP/IDA, especially in the chelating ability for alkaline earth metals. The resin with a longer spacer (CCS-HP/IDA) showed higher adsorption selectivity between heavy metal ions and alkaline earth metals at pH < 7. The separation efficiency of the major matrix cations in seawater (Na. K, Mg, Ca) has also been investigated, and matrix interference was negligible even in a seawater sample at pH 5 with CCS-HP/IDA. The recoveries of Mn at pH 5 with CCS-HP/IDA or Chelex-100 were almost 100%. However, those of Mg with each resin were 4 or 98%, respectively. The adsorption capacities of synthesized CCS-HP/IDA for Cu(II), Pb(II) and La(III) were 0.90, 0.65 and 0.34 mmol g(-1), respectively. Therefore, the chelating chitosan resins developed are applicable to the pretreatment of trace amounts of elements in various kinds of water samples.