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Progress in clean techniques that includes clean sampling, storage, treatment and analysis of seawater samples is essential for the exact determination of trace elements in seawater. Japanese marine chemists have worked vigorously to establish clean techniques and the accumulation of data. Results have met with a measured amount of success, as briefly shown in this review paper. The behavior and distribution of trace elements in seawater are dependent on multifaceted chemical, physical and biological processes occurring in the ocean. Thus, the chemical speciation of inorganic and organic species of trace elements in seawater has been eagerly studied. Specifically, the dissolved states of oxyacid elements such as Cr, I, Se, Te, As and Sb have been determined by using various procedures and methods developed by Japanese marine chemists. The present paper reviews the procedures of chemical speciation for inorganic species of Cr, I, Mn, Mo/ W, Se, Te, As and Sb as well as those for organic species of Cr, Ge, I, Se, Hg, Fe and Cu in seawater. The difficulty in obtaining exact measurements of the total concentrations of trace elements in seawater is shown concerning Fe, Cu, Zn and Se as examples.

Colorimetric determination of fluoride ion in drinking water was done with a long capillary cell (LCC) (length: 0.7–4 m). When a solution whose refractive index exceeds that of the cell material (Pyrex=1.474) is put into the capillary, a wave-guide(total reflection) cell is obtained, its transmissibility to source light is independent of cell shape. Color development was based on the La-ALC method: Lanthanum-alizarin complexone was added to the sample. The fluoro-lanthanum-alizarin complexone which formed was combined with N,N-diethyl-aniline and extracted into isoamyl alcohol. Fluoride complex extracted to isoamyl alcohol was mixed with a mixture of carbon disulfide and acetone (the final refractive index of analyte solution=1.57). Extension of cell length longer than 1 m provided highly sensitive colorimetry. Enhancement of absorption was 0.5–2.5×103times in magnitude by using 4 m LCC. Detection limit and recovery of this method were 10 ng/l and 93–104% (for 50 μg/l), respectively. The present method was applied to the determination of fluoride in drinking water collected around Tokyo.