Seawater methylated compounds

The biological cycle of arsenic in the surface ocean involves the uptake of arsenate by plankton, the conversion of arsenate to a number of as yet unidentified organic compounds, and the release of arsenite and methylated species into the seawater. Biological demethylation of the methyl-arsenicals and the oxidation of arsenite by as yet... 

Eberhardt and Sieburth [133] also devised a spectrophotometric procedure for the determination of aldehydes in seawater. The method is based on the reaction of aldehydes with 3-methyl-2-benzothiazolinone, hydrazone hydrochloride, and ferric chloride to produce a coloured compound. A detection limit of0.072 jlM formaldehyde per litre was obtained using a 5 cm path-length. 

Leek and Baagander [311] determined reduced sulfide compounds in seawater by gas chromatography using a flame ionisation detector. Substances determined include methyl mercaptan, dimethyl sulfide, hydrogen sulfide and carbon disulfide. Detection limits range from 0.2ng/l (carbon disulfide) to 0.6 ng/1 (methyl mercapton). 

The high sensitivity and selectivity of some gas chromatographic detectors are used to advantage in the measurement of organic mercury compounds. In the simplest approach, methyl mercury is extracted from seawater and converted to the iodide for electron capture gas chromatography [74],... 

The generation and recovery of stannane, methyl-, dimethyl-, and trimethyl-stannane were studied in seawater. Average tin recoveries for the six samples analysed, to which were added 0.4-1.6 ig methyltin compounds and 3ng inorganic tin, ranged from 96 to 109%. Reanalysis of analysed samples shows that all methyltin and inorganic tin is removed in one analysis procedure. 

Bromine occurs in nature as bromide in many natural brine wells and salt deposits. It also is found in seawater at a concentration of 85 mg/L. The element was discovered by A. J. Balard and C. Lowig, independently in 1826. Bromine is used in bleaching fibers and as a disinfectant for water purification. Other appbcations are in organic synthesis as an oxidizing or brominat-ing agent in the manufacture of ethylene dibromide, methyl bromide and other bromo compounds for dyes and pharmaceutical uses as a fire retardant for plastics and in chemical analysis. Ethylene dibromide is used in anti-... 

The chemical shifts in the NMR for the methyl groups on arsenic can vary depending on pH. They are, however, sufficiently different from each other and from other marine arsenic compounds that they are readily distinguishable even in seawater solutions (Fig. 1). Thus, the possibility exists for examining marine arsenic transformations in solutions or cells by NMR spectroscopy. Little work has been done in this area. 

Leek and Bagander [342] determined reduced sulphur compounds (hydrogen sulphide, methyl mercaptan, carbon disulphide and dimethyl sulphide) in seawater by gas chromatography using flame detection. Detection limits ranged from 0.2ng L 1 for carbon disulphide to 0.6ng L 1 for methyl mercaptan. Hydrogen sulphide was determined at the... 

As a photochemical oxidation product of DMS (Bentley et al., 1971) dimethyl sulphoxide may be detected in seawater which has been reported to inhibit photosynthesis in algae (Cheng et al., 1972). Methionine and biotin sulphoxides are oxidation products of methionine and biotin respectively, while microorganisms have been reported which reduce these compounds as well as DMDS (Zinder and Brock, 1978b). These authors also comment on the chemical stability of the sulphones. The methyl sulphones which have been identified in Baltic seal by Jensen and Jansson (1976) are, however, metabolically produced from PCB and DDE within the animal. 

---