Synthesis And Application Of Novel Chelating Adsorbents To On-line Column Preconcentration And Separation Of Noble Metals

Owing to its advantages of faster analysis, better precision, lower consumption of reagents and sample and readily automated operation, the on-line microcolumn preconcentration and separation technique have undergone rapid development since its advent in early eighties. It has a indispensable importance for the determination of trace and ultra-trace amount of analyte and complicated samples. A lot of research papers about it have been published and there have been commercial instruments available. However, the adsorbents used for this purpose are mainly commercial ion-exchange resins and other adsorbents such as activated carbon and activated alumina. Hence, the synthesis and selection of suitable adsorbents are one of the most important tasks for improving the technique. The literature about the synthesis of the ion exchange and chelating adsorbents used in the off-line separation and preconcentration of the noble metals and the development of the on-line microcolumn separation and preconcentration of the noble metals were reviewed. Four silica gel-based adsorbents with rhodanine, 2-mercaptopyrimidine, 2-mercaptothiazoline and isophenylthiourea as the functional groups were first synthesized and applied to the on-line separation and preconcentration of silver, gold, palladium and platinum for their FAAS determination. The results demonstrated that all these adsorbents could quantitatively adsorb these noble metal ions rapidly from strong acid media and the ions adsorbed could be desorbed by thiourea solution. Common cations and anions did not interfere with the adsorption and determination of these four noble metal ions except that high concentration of Cl-interfered with the adsorption of silver with the first three adsorbents. There was no interference among these four ions each other too. The sensitivity can reach or exceed the level of GFAAS at the sampling frequency of 20~60 h-1. Meantime, faster desorption was achieved in the use of adsorbents with smaller adsorption capacity. Smaller adsorption capacity did not conflict with better interferent tolerance if a high selective chelating group is bonded. So glass bead was first used as surppot used in the flow injection on-line microcolumn separation and preconcentration. An amidinothiourea imbilized glass bead was synthesized and applied in the...