Preconcentration and Determination of Trace Metals in Seawater Using a Thiol Cotton Fiber Minicolumn Coupled with Inductively Coupled Plasma Mass Spectrometry

Abstract

Direct determination of trace metals in seawater is a difficult task, not only because the concentration of many trace metals is close to or below the detection limits of most of the analytical instruments, but also the seawater matrix may cause serious interference for determination. Preconcentration and separation can solve these problems. There are many preconcentration methods, which include ion exchange, precipitation, solvent extraction and solid phase extraction. Among them the most commonly used method is solid phase extraction, 1-7 which enables preconcentration of trace metals from larger volumes of sample, reduction and/or elimination of matrix interferences, prevention of contamination, in-situ or online coupling with various detectors.If one compares fibers with other solid phase extraction materials, fibers have higher specific surface areas, approximately two orders of magnitude larger than that of a gelstructure granular ion-exchanger or 5 -6 times that of a porous copolymer. 8 Fiber also differs from crosslinked granular polymers in the presence of linear or branched macromolecules, which might have swelling capacity. Thus fibrous ionexchangers have good kinetic and mechanical characteristics. 9 Thiol cotton fiber (TCF) is a well-characterized chelating ion exchange fiber.Previously, Nishi developed TCF to preconcentrate trace methyl mercury in water.10 Gómez et al. determined Au and Ag(I) in the aquatic environment at the µg l -1 levels by applying TCF. 11 Seawater contains relatively high dissolved salt content (typically about 3.5%) and very low concentrations of trace metals. Therefore, analysis of trace metals in seawater is always a challenge. What we are interested in is whether TCF could be used to separate and preconcentrate trace metals in seawater. On the other hand, online techniques offer more advantages than the conventional manual batch procedures, i.e. better reproducibility and accuracy, higher sample throughput, lower consumption of reagent, prevention of contamination and easily automated operation.12-15 Therefore, it has a bright future for both laboratory and field usage. Whether TCF could be packed in the minicolumn and developed as an online column preconcentration technique is another area of research interest.In this work, an online preconcentration system was developed by using a TCF minicolumn coupled with ICP-MS for preconcentration and determination of trace metals Cu, Pb, Zn and Cd in seawater. Preconcentration parameters, including seawater sample pH, flow rate, preconcentration volume, eluent flow rate, eluent concentration and eluent volume, were experimentally optimized. The precision and accuracy of the method was demonstrated by the analysis of seawater certified reference materials CASS-4 and NASS-5. Experimental Reagent and solutionStock solutions of Cu, Pb, Zn and Cd, 1000 mg l -1 were prepared by dissolving an appropriate amount of metal oxide (Specpure, Johnson Matthey Chemicals) in nitric acid (67%, 5.0 ml).Single and multi-element standard solutions of ...

Multiple-Element Detection in Aqueous Solution and Seawater by Using an On-line Preconcentration Method for Inductively Coupled Plasma Mass Spectrometry

“…As compared to the ion-exchange resin method, [26][27][28] or an electrothermal vaporization coupled with the on-line preconcentration-ICP-MS apparatus, 29,30 the detection limits for the elements studied in this work were either comparable to or worse than by an order of magnitude. Ion-exchange resins usually require a strong acid mixture as an eluent.…”

Metals in biology: defining metalloproteomes

“…The recent development of practical instruments for inductively coupled plasma mass spectrometry (ICP-MS) has made possible rapid and sensitive quantification of metals from complex biological samples. Quantitative ICP-MS metal analysis is a powerful analytical approach for metals in broadly diverse samples such as honeybee venom [27], urine and plasma [28,29], seawater [30], and quantifying toxic metal accumulations in seafood and drinking water [31,32]. As these metallo-approaches become more commonly applied, they will undoubtedly help identify markers of human disease much like the more mature proteomic [33] and metabolomic [34] approaches.…”

Trace Element Determination by ICP‐AES and ICP‐MS: Developments and Applications Reported During 2004 and 2005

“…Xu et al (2003) have developed an automated online liquidliquid extraction procedure to preconcentrate REE (Er, Eu, La, Nd, Sm, Y, Yb) before ICP-AES measurement. An online separation and preconcentration procedure for metals in seawater (Cu, Zn, Cd and Pb) used a mini-column packed with thiol cotton fibre (TCF) and coupled to an ICP-MS (Zhang et al 2005). The organic phase was then injected into the ICP-AES for measurement.…”

“…There were good recoveries of spiked elements in reference seawater samples (NRCC CASS-3 and NRCC NSS-5) and simulated wastewaters (CWW-TM-A), except for Cu, where elevated recoveries were attributed to reagent contamination. An online separation and preconcentration procedure for metals in seawater (Cu, Zn, Cd and Pb) used a mini-column packed with thiol cotton fibre (TCF) and coupled to an ICP-MS (Zhang et al 2005). The procedure was optimised for sample pH, flow rate and volume, as well as eluent (HCl) flow rate, concentration and volume.…”