Preconcentration of Trace Cadmium from Seawater Using a Dynamically Coated Column of Quaternary Ammonium Salt on C18-Bonded Silica Gel and Determination by Graphite-Furnace Atomic Absorption Spectrometry

Abstract

The determination of trace elements in environmental waters is increasing in contamination studies, owing to the need to guarantee the good quality of water for various purposes. For the determination of Cd in water samples, graphite-furnace atomic absorption spectrometry (GF-AAS) is the chosen method of many analysts because of its relative simplicity, the possibility of automation and the low instrumental detection limits given. However, for complex samples such as seawater, there are important problems: firstly, matrix interference from the salt matrix remains, which causes a deterioration in the accuracy and precision. Secondly, a previous preconcentration of Cd is required, because of the very low concentration of cadmium in the surface seawater.1 Thus, a different preconcentration procedure, e.g., coprecipitation 2 , solvent extraction 1,3 , sorption on chelating resins 3,4 or immobilized adsorbents 5-8 , have been proposed to preconcentrate and separate cadmium from the seawater matrix. However, most of the procedures involve several chemical stages, including a laborious pH adjustment in order to remove any interfering matrix, thus increasing the possibility of a loss of the analyte and sample contamination. Recently, a column of a reversed-phase substrate loaded with hydrophobic molecules, such as bis(2-ethylhexyl)-hydrogen phosphate and 2-ethylhexyldihydrogen phosphate 10 , tris(2,6-dimethoxyphenyl)phosphine 11 and quaternary ammonium salts 9,12 , has been prepared to develop a preconcentration method for trace elements in acidic solutions. These materials were used for the preconcentration of rare-earth elements 10 and Cd 12 in seawater by column techniques. Previously, we 13 proposed a new preparation technique of a dynamically coated column involving C 18 -bonded silica gel (C 18 ) coated with methyltricaprylylammonium chloride (Aliquat 336). The column was applied to the matrix isolation and preconcentration of platinum 13 and zinc 14 in environmental samples. This paper describes a simple and convenient method for the selective preconcentration of trace cadmium from seawater, followed by an atomic absorption spectrometric determination of the element. The precision and accuracy of the method were demonstrated by analyzing certified reference materials. The process of preconcentration is simple, easily yields a large enrichment factor, requires no buffer and results in a low contamination of the blank. Experimental ApparatusAtomic absorption analyses were performed on a Perkin-Elmer (Model 4100ZL) atomic absorption spec- Applied and Environmental Chemistry, Kitami Institute of Technology, Kitami, Japan **Muroran Institute of Technology, Muroran, Japan ***Hokkaido Institute of Environmental Sciences, Sapporo, Japan A dynamically coated column of C18-bonded silica gel with methyltricaprylylammonium chloride was used for the selective preconcentration of Cd from water samples under acidic conditions. The complete adsorption of Cd occurred from seawater with no additional reagent, and was found f...

Simplified method for determining cadmium concentrations in rice foliage and soil by using a biosensor kit with immunochromatography

“…Thus the rate of Cd recovery from rice foliage seems to increase with increasing concentration of the HCl solution used. However, elevation of the HCl concentration in the extract affects the subsequent process of purification by the chelate column: not only Cd, but also Zn, is trapped in the column 5…”

“…Cadmium retained in the column was eluted with 5 mL of 0.05 mol L −1 HNO 3 . The column was prepared based on Akatsuka's method 5…”

Immunochromatography for the rapid determination of cadmium concentrations in wheat grain and eggplant

“…5B, Advantec Toyo, Tokyo, Japan), and 1 mL of each filtrate was passed through an ion exchange column (SEP‐01, Sumika Chemical Analysis Service, Osaka, Japan), where Cd was trapped selectively. This column was designed on the basis of Akatsuka et al 's method 8. It is believed that Cd forms a chloro‐complex and is trapped selectively by the column.…”

“…With this test, Cd in brown rice was extracted with HCl, and the extract was purified on a chelate silicagel column prepared based on Akatsuka et al 's method8 to remove other metals. The pretreated solution was then diluted with buffer for neutralization and tested with the immunochromatographic assay 6.…”

Cadmium Purification and Quantification Using Immunochromatography

“…Immunochromatography Measurements. For cadmium concentration measurement by immunochromatography, cadmium in HCl extracts was purified by the quaternary ammonium salts employed in a chelating column that was designed on the basis of Akatsuka's method (17 ). Five milliliter HCl extracts of each sample were passed through the chelating column.…”