Fresh water by atomic absorption

Extraction Techniques for the Determination of Cobalt, Nickel, and Lead in Fresh Water by Atomic Absorption... 

Courtot-Coupez and Le Bihan [209,210] determined non-ionic detergents in sea- and fresh-water samples at concentrations down to 2 pg/1 ppm by benzene extraction of the tetrathiocyanatocobaltate (II) (NH4)2 (Co(SCN)4) [ 182] detergent ion-pair, followed by atomic absorption spectrophotometric determination of cobalt [209]. 

The detection limits for cobalty nickel, and lead in aqueous solution by atomic absorption are about 50 fig. per liter. Normally these elements occur at lower concentrations in fresh waters, and direct measurement by atomic absorption is not possible. A rapid, simple, accurate, and sensitive chelation-extraction method for determining lead, cobalt, and nickel is attained by chelating the metals with ammonium pyrrolidine dithiocarbamate at a pH of 2.8, extracting the metal-chelates with methyl isobutyl ketone, and aspirating the ketone layer. Results obtained by this method agreed well with results obtained by spectrographic methods. As little as 1 fig. of lead, cobalt, and nickel per liter can be detected. This is at least one order of magnitude lower than most other wet chemical procedures. 

A tomic absorption is being used routinely for the direct determination of sodium, potassium, calcium, magnesium, and several trace elements strontium, lithium, manganese, copper, and zinc in natural vaters (4). There is ordinarily no need to concentrate these trace elements since most waters contain detectable amounts. However, certain other trace elements, such as cobalt, nickel, and lead normally occur in fresh waters at concentrations less than can be detected by atomic absorption directly. 

Le Bihan and Courtot-Coupez [186] analysed fresh water for cationic detergents by a method based on atomic absorption spectrometry of the copper-detergent complex. 

Agemian and Chau [55] have described an automated method for the determination of total dissolved mercury in fresh and saline waters by ultraviolet digestion and cold vapour atomic absorption spectroscopy. A flow-through ultraviolet digester is used to carry out photo-oxidation in the automated cold vapour atomic absorption spectrometric system. This removes the chloride interference. Work was carried out to check the ability of the technique to degrade seven particular organomercury compounds. The precision of the method at levels of 0.07 pg/1, 0.28 pg/1, and 0.55 pg/1 Hg was 6.0%, 3.8%, and 1.00%, respectively. The detection limit of the system is 0.02 pg/1. 

As shown in Figure 6.49a, the cracks grow by slip dissolution due to diffusion of active water molecules, halide ions, etc., to the crack tip, followed by a rupture of the protective oxide film by strain concentration, fretting contact between the crack faces. This is followed by dissolution of the fresh exposed surface and growth of the oxide on the bare surface. For the alternative mechanism of hydrogen embrittlement in aqueous media, the critical steps involve diffusion of water molecules or hydrogen ions to the crack tip reduction to hydrogen atoms at the crack tip surface diffusion of adsorbed atoms to preferential surface locations absorption and diffusion to critical locations in the... 

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