Seawater compound identification

While there has always been some interest in the nature of the organic compounds in seawater, identification of actual compounds has progressed slowly because of the low concentrations present. With a total organic carbon concentration of 0.5 -1.5 mg/1 of carbon, the total concentration of any single organic compound is likely to be less than 10 7 M. Therefore, in the past, identification of individual compounds has been limited to those few for which specific, sensitive chemical methods existed. These methods were usually spectropho-tometric, and were often developments of methods originally used in clinical chemistry. 

In the shore laboratory, the samples must be handled with the care needed for any trace analysis. It must be remembered that the total amount of organic carbon in seawater is around 1 ppm single compounds are likely to be present at ppb levels. In order to collect enough material even for positive identification of some of the compounds present, the materials must often be concentrated. 

An analysis performed by gas chromatography can usually also be performed by coupled gas chromatography-mass spectrometry, often with some increase in sensitivity, and with considerably greater certainty in the identification of the compounds. This technique has been applied to seawater [415] and to marine sediments [416]. 

If we look at the intercomparison studies that have been made on the measurement of lead in seawater [21], two points become obvious first, that almost no one can measure lead accurately in seawater and second, that there is much less lead present than anyone had estimated. With so little lead present in any form, identification of the organic moiety of an organolead compound becomes a major problem. 

J.-F. Rontani (1991). Identification by GC/MS of acidic compounds produced during the photosenitized oxidation of normal and isoprenoid alkanes in seawater. Int. J. Environ. Anal Chem., 45,1-9. 

The low concentrations of free sterols in ocean waters require that large volumes of seawater are extracted in order to decrease the detection limit for FID detection. The structural similarity of the sterol compounds found in seawater makes demands on the chromatographic separations and identification, which may only be reasonably met with the use of the GC—MS systems (e.g. Gagosian and co-workers Saliot and co-workers). 

It seems evident that to achieve pheromone identification, a clear biological assay relying upon unambiguous behavior coupled with a chemical identification strategy, testing each successive purification step, is critical. Additionally, the use of biologically relevant samples such as conditioned seawater that contains compounds released into the environment at biologically relevant concentrations should be used. 

Abundant Cis isoprenoid ketone, Z/E pristenal, and Z/E phytenal as well as phytol biomarker compounds were detected in the sinking particulate materials from the Yongshu Reef Lagoon and the continental shelf of the East China Sea (Figs. 5.28 and 5.29). This appears to be the first report of these compounds in China marine environment. Detection of these compounds in the studied regions is of some importance to understand the evolutional processes of acyclic isoprenoid compounds in the seawater column and their formative pathways in marine sediments. Their identifications were based on chromatographic retention time, mass spectrum features (Figs. 5.28 and 5.29), and comparison with those reported previously. The mass spectrum of phytol trimethylsilyl ether exhibits a base peak at mlz 143 and a molecular ion at mjz 368. Cig isoprenoid ketone has a base peak at mjz 58, a molecular... 

Besides TSP-spectra from organophosphorus and different groups of polar pesticides, APCI, ESI, FAB and PBI spectra were presented. CID allowed the identification of pesticide residues and the confirmation and quantification of these compounds by TSP at concentrations < 100 ng L [175]. Barcelo et al. [239] extracted river water and spiked seawater samples by Cig Empore disks to concentrate orga-nophosphoras pesticides prior to identification and quantification while Bagheri et al. [247] for the same purpose used on-line SPE for phosphorus pesticides and TSP-LC-MS. 

Kristiansen NK, Froshaug M, Aune KT et al (1994) Identification of halog ated compounds in chlorinated seawater and drinking-water produced offshore using n-ptmtane extractitm and open-loop stripping technique. Environ Sci Technol 28 1669-1673... 

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