Preconcentaration/separation methods for the multi-elements analysis of trace metals.

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 10650791
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 工業分析化学
• Research Institution: Kitami Institute of Technology
• Principal Investigator: AKATSUKA Kunihiko Kitami Institute of Technology, Department of Applied and Environmental Chemistry, Professor, 工学部, 教授 (50003182)
• Project Period (FY): 1998 – 1999
• Keywords: Preconcentration method / trace metals / solid phase extraction / water-soluble complexes / chemically-bonded silica gel / chelating resin / ICP-MS analysis / multi-elements analysis

Research Abstract

Some methods are proposed for the analysis of ultra-trace metals in environmental samples by atomic spectrometry after preconcentration/separation with solid phase extraction. The one method is based on the formation of water-soluble complexes in an aqueous sample followed by adsorption onto a CィイD218ィエD2-bonded silica gel column. 2-(5-Bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (5-Br-PAPS) was used as a water-soluble chelating reagent. By passage of water sample, added 5-Br-PAPS and adjusted the pH at 8.3, quantitative adsorption of trace metal complexes onto the column took place while the major matrix ions such as alkaline and alkaline earth metal ions, passed through the column. The metals were subsequently eluted with 4.0 ml of 1.0 M HNOィイD23ィエD2. Seven trace metals (Mn, Fe, Ni, Cu, Zn, Cd and Pb) were determined with an ordinal plasma ICP-MS. The ultratrace of Fe was determined by nitrogen-argon mixed gas plasma to reduce the isobaric interference by ィイD140ィエD1ArィイD 116ィエD1O on ィイD156ィエD1Fe. The precision and accuracy of the method were demonstrated by analyzing coastal and open-ocean seawater CRMs : CASS-2 and NASS-4 (NRC, Canada). Ethylenediaminetriacetate-bonded silica gel (ED3A-SG) is also proposed as a solid phase extractant in the other method. ED3A was synthesized by reacting silica gel with N-(trimethoxysilylpropyl)ethylenediaminetriacetate. Sixty ml of 5% aqueous solution of the silane coupler added to 18 g of dried silica gel and stirred for 3 h, then silica gel was filtered off and dried for 24 h. The metal uptake capacity of ED3A-SG thus obtained was 0.18 mM gィイD1-1ィエD1 and remained the capacity for at least 3 months when it was stored in a desiccator at room temperature. After rinse the ED3A-SG column with 1.0 M HNOィイD23ィエD2 and water, a definite volume of aqueous sample, the pH of which was adjusted with acetic acid or ammonia, was percolated through the column to concentrate trace metals. The metals collected onto the column was eluted with 5 ml of 1.0 M HNOィイD23ィエD2. The eluate was then analyzed by ICP-MS. More than 15 metals including Fe, Co, Ni. Cu. Zn. Cd and Pb were quantitatively collected onto the column between pH 3.5 and 4.5. Whereas major matrices such as alkaline and alkaline earth metals were not collected at this pH region. The proposed method was applied to determine trace metals in environmental water samples such as river waters, coastal seawater and tap water. Those methods proposed here achieved rapid and reliable preconcentration/separation of trace metals and elimination of matrix effects in the analysis of environmental water samples by ICP-MS. The procedures involve simple chemical separations with less contamination and provide improvements of the detection power necessary for trace metals in environmental waters.