OFFLINE AND ONLINE SOLID PHASE EXTRACTION/PRECONCENTRATION OF INORGANICS

Solid phase extraction (SPE) is a powerful technique for preconcentration/removal or separation of trace and ultra trace amounts of toxic and nutrient elements. SPE effectively simplifies the labour intensive sample preparation, increase its reliability and eliminate the clean up step by using more selective extraction procedures. The synthesis of sorbents with a simplified procedure and diminution of the risks of errors shows the interest in the areas of environmental monitoring, geochemical exploration, food, agricultural, pharmaceutical, biochemical industry and high purity metal designing, etc. There is no universal SPE method because the sample pretreatment depends strongly on the analytical demand. But there is always an increasing demand for more sensitive, selective, rapid and reliable analytical procedures. Among the various materials, chelate modified naphthalene, activated carbon and chelate functionalized highly cross linked polymers are most important. In the biological and environmental field, large numbers of samples are to be analysed within a short span of time. Hence, online flow injection methods are preferred as they allow extraction, separation, identification and quantification of many numbers of analytes. The flow injection online preconcentration flame AAS procedure developed allows the determination of as low as 0.1 µg/l of nickel in soil and cobalt in human hair samples. The developed procedure is precise and rapid and allows the analysis of 30 samples per hour with a loading time of 60 s. The online FI manifold used in the present study permits high sampling, loading rates and thus resulting in higher preconcentration/enrichment factors of -725 and 600 for cobalt and nickel respectively with a 1 min preconcentration time compared to conventional FAAS signal. These enrichment factors are far superior to hitherto developed on line preconcentration procedures for inorganics. The instrumentation adopted in the present study allows much simpler equipment and low maintenance costs compared to costlier ICP-AES or ICP-MS instruments

Quinoline-8-thiol functionalized solid phase extractant for the preconcentration of ultratrace amounts of mercury (II)

569-572A solid material consisting of quinoline-8-thiol functionalized naphthalene provides a convenient, rapid and economical method for preconcentration of mercury. The mercury-quinolinc-8-thiol complex is quantitatively retained on naphthalene in the pH range 5.0-7.0. The solid mixture consisting of the metal complex together with naphthalene is dissolved in 2 ml of acetone and mercury content established spectrophotometrically. The calibration graphs are linear over the mercury concentration range 0.002-0.2 μg/ml. Ten replicate determinations of 1.0 μg of mercury present in 250 ml of solution gave a mean absorbance of 0.02 with a relative standard deviation of 3.1 %. The detection limit (corresponding to 3 times the standard deviation of the blank) and enrichment factors are found to be 0.001 μg/ml and 125 respectively. The accuracy of the developed preconcentration procedure has been tested by analyzing human hair standard reference material and human hair samples