Silica, generally metal analysis samples

The problem of analyzing water samples is essentially no different from that of analyzing aqueous solutions in general. You are referred to Ref. 4 for a compilation of some of the many commonly analyzed substances in water and the procedures employed for their analysis. Measurements made include acidity or alkalinity, biochemical oxygen demand, carbon dioxide, chlorine, dissolved oxygen, electrical conductivity, fluoride, particulate and dissolved matter, ammonia, phosphate, nitrate, silica, sulfate, sulfite, sulfides, turbidity, various metal ions, bacteria, microorganisms, and so forth. 

Para-substituted, X = H, CH3, OCH3, Cl, and NO2, dithioacetal derivatives were synthesized and chemically immobilized onto the surface of silica gel for the formation of five newly modified silica gel phases. The metal sorption properties of these silica gel phases were studied and the results revealed a general rule of excellent affinity for the selective extraction of Hg(II) in the presence of other interfering metal ions, giving rise to a range of 94-100% extraction of the spiked Hg(II) in the metal ion mixture. The potential applications of these modified silica gel phases for selective extraction of Hg(II) from two different natural water samples by a column technique, followed by cold vapor atomic absorption analysis, were also studied. The substituent effect on the process of selective extraction of Hg(II) by the modified silica gel phases was also presented. The structures of silica gel-immobilized-dithioacetals are given in Scheme 19. 

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