Analytical procedures organic reagents

Methods involve extractions of analytes into organic solvents, as well as treatments with acidic or basic reagents. Solid-phase extraction can be used for removal and pre-concentrations of analytes in aqueous solutions. Applications of low-power focused microwave technology have been investigated as a means of dissolution, and good results have been reported for extractions of organometal-lic compounds of tin and mercury (Schmitt et al., 1996 Szpunar et al., 1996). Analyses of CRMs were used for verification. The time necessary for quantitative isolations of the analytes was greatly reduced, e.g. 24 h to 5 min. In addition, there were reductions in solvent volumes, and improvement in analyte recoveries. Some of the analytical procedures for speciation of particular elements such as mercury, described later in this chapter, include microwave-assisted sample preparation. 

Fig. 13 shows an example of how important it is to avoid contamination, and its influence on the final result of the analysis. The analytical procedure was a pre-concentration of aluminum by adsorption of its complex with an organic reagent (chrome azurol S) onto a polymeric material (polyethylene powder) packed into a column. Standard solutions were prepared and the procedure carried out after adopting stepwise precautions to avoid contamination. It can be seen that, only after adopting all steps, was the contamination controlled. The graph also shows that the lower the aluminum content in the sample the higher is the contribution of the contamination sources. 

Fiber-optic sensors, particularly fluorescent sensors, have become the object of considerable interest among researchers. The action of most fluorescent sensors is based on the change in the fluorescence properties of organic reagents immobilized on a solid matrix upon contact with solutions of metals in a continuous system. Zelters et al. [187] studied the immobilization and complex formation of immobilized Morin with zirconium and tin in order to develop a procedure for sorption fluorimetric determination of these elements. The selection of polyoxiflavones for immobilization was determined as a valuable analytical procedure. 

Analytical procedure. The urine is collected in polyethylene bottles and mixed with acetic acid (1 mL acetic acid to 100 mL urine), and the specimens are refrigerated until use. A 4 mL sample of urine is placed into a disposable polyethylene centrifuge tube with 0.5 mL extraction solution and shaken mechanically for 5 min, then centrifuged at 3000 min at 20°C. The organic phase is analyzed by GFAAS. A reagent blank is run with each analytical series. 

The determination of small amounts of organic compounds in complex matrices has long been a difficult analytical problem. If separation procedures are used they frequently need to be complex and are time consuming. By using specific binding reagents, RIA methods avoid such difficulties and facilitate the analysis of many compounds at picogram levels... 

Having as necessary, dried, homogenized or comminuted the samples, they must now be digested in a suitable reagent to extract elements in a suitable form for chemical analysis. In many organizations we have reached the point where the analyses pass from the hands of the person who took the sample to those of the analytical chemist. In the author s experience, however, it must be emphasized that to ensure best-quality results the whole procedure from, for example, statistically sampling a sediment to the final chemical analysis, should be handled by the same person. 

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