Offline and online solid phase extraction/preconcentration of inorganics

Abstract

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. Chapter 1 deals with general introduction to solid phase extractive preconcentration and techniques adopted for the preconcentration. Chapter 2 describes the determination of mercury (II) in Biological samples, such as hair using quinolin-8-thiol modified naphthalene as a solid phase extractant. The preparation of above mentioned material is very simple and the mercury (II) coprecipitated on naphthalene is simply dissolved in acetone for subsequent determination using dithizone procedure. Various parameters that influence the preconcentration of mercury (II) by solid phase extraction are systematically optimized and results obtained are discussed in this chapter. Chapter 3 concerns with the removal of mercury (II) from hazardous wastes particularly brine sludge and effluent of chlor alkali industry with the use of solid phase extractant 1-(2-thiazolylazo)napthol (TAN) sorbed activated carbon. Various optimization studies are described in detail along with a flow chart. Chapter 4 describes the selective preconcentration of uranium (VI) using Diarylazobisphenol modified activated carbon as solid phase extractant. The preparation of Diarylazobisphenol modified activated carbon is simple, and the uranium (VI) sorbed on Diarylazobisphenol modified naphthalene was eluted with suitable reagent for subsequent determination by spectrophotometry using Arsenazo III procedure. Various parameters that influence the preconcentration of uranium (VI) by solid phase extraction were systematically optimized, and its accuracy was tested by analyzing marine sediment reference material (MESS-3). Furthermore, the applicability of the procedure for determining uranium (VI) in soils and sediments are described. Chapter 5 concerns with synthesis and characterization of the resin Amberlite XAD-4 functionalized with various β-diketones and its application in an off line preconcentration of thorium (IV) in column mode from a host number of other lanthanide elements (Rare earth chlorides). Since, Amberlite XAD-4 polymeric adsorbent has excellent physical, chemical and thermal stability, this SPE material can be reused via repeated cycles to preconcentratively separate thorium (IV) from dilute solutions. The influence of various cations and anions on the preconcentration of thorium (IV) has been studied. Furthermore, the thorium (IV) content in rare earth chloride has been established by using the above method. Chapter 6 concerns with the development of on-line flow injection-flame atomic absorption spectrometry (FI-FAAS) technique for the determination of cobalt and nickel at µg/l level, using commercially available c18 bonded silica gel microcolumn loaded with orthodihydric phenols. The preconcentration and elution sequence is highly reproducible. One minute loading allows a sampling frequency of 30/h. In addition, a linear relationship was observed between loading time and enrichment factor and thus enhancing sensitivity at the expense of number of samples that can be analysed in an hour. The validity of the developed method carried out by analyzing certified Hair reference materials soil and sediments for cobalt and nickel. Again, the developed method has been applied successfully to the analysis of real human hair, soils and sediment samples collected at various geographical locations. Chapter 7 concerns the conclusions and suggestions for the future work based on the results obtained in the present investigations.