Trace metals selective sorbents

An on-line concentration, isolation, and Hquid chromatographic separation method for the analysis of trace organics in natural waters has been described (63). Concentration and isolation are accompHshed with two precolumns connected in series the first acts as a filter for removal of interferences the second actually concentrates target solutes. The technique is appHcable even if no selective sorbent is available for the specific analyte of interest. Detection limits of less than 0.1 ppb were achieved for polar herbicides (qv) in the chlorotriazine and phenylurea classes. A novel method for deterrnination of tetracyclines in animal tissues and fluids was developed with sample extraction and cleanup based on tendency of tetracyclines to chelate with divalent metal ions (64). The metal chelate affinity precolumn was connected on-line to reversed-phase hplc column, and detection limits for several different tetracyclines in a variety of matrices were in the 10—50 ppb range. 

The determination of heavy metals at trace levels is important in the field of environmental analysis. This problem can be solved by the help of highly selective sorbents. 

Co, Cr, Ni, Cu, Zn tap, drinking, waste A plethora of kinetic catalytic procedures for trace metal monitoring has been developed Sorbent preconcentration sometimes used A variety of speciation schemes based upon the selective complexation of particular oxidation states has been designed... 

Adsorption of trace elements in cationic form is pH-dependent and is characterized by a pH range, where the amount of a heavy metal that is bound to a sorbent increases abruptly to nearly 100%, known as adsorption edge. Fig. 1 shows the adsorption of Pb, Cu, Zn, and Co at different pH values onto selected short-range-ordered oxides (a noncrystalline A1 precipitation product [RO], ferrihydrite [Roo], and mixed Fe-Al oxides formed at different initial Fe/Al molar ratios [Rl-RlO]) (Table 1), whereas Fig. 2 shows the adsorption of Cu onto well-crystallized metal oxides, goethite, and bayerite. In the region in which adsorption increases rapidly, the species MeOH and Me(OH)2 of each metal were negligible. 

A new silica gel-based chelating sorbent, with thiourea as a functional group, was used for the FI online preconcentration and separation of trace levels of silver, gold, and palladium. The selected metal ions were adsorbed onto a column packed with thiourea-modified silica gel (TuSG). The sorbent exhibited excellent stability and the sorption properties of TuSG did not change after 1000 cycles of use. The selected metals in a secondary nickel alloy, an anode slim, an electrolytic solution, and three national certified ore samples were determined satisfactorily using the proposed method. ... 

---