The behavior of methylene blue (MB) molecules at silica/water and silylated silica/water interfaces was examined using visible attenuated total reflection spectroscopy with a slab optical waveguide (SOWG). An alkyl silane coating changed the adsorbed form of MB on the surface from a dimer (lambda max = 600 nm, bare silica surface) to a monomer (lambda max = 670 nm), and the carbon number of the silylation reagent influenced the amount of adsorption and the orientation of the molecule. Moreover, the addition of an anionic surfactant, dodecylbenzenesulfonate (DBS), caused the deposition of MB/DBS ion pairs, which gave an identical attenuated total reflection (ATR) spectrum to that of the dimer. Linear dichroism measurements revealed that the ion pairs were adsorbed onto the silylated silica surface randomly in terms of the orientation angle of MB, while the MB monomer was strongly oriented, i.e., the direction of the transition moment of MB roughly parallels the surface plane. This difference in the orientation angles of the adsorbed species can be utilized for their selective detection using polarization SOWG measurements.

Cation exchange and size exclusion high-performance liquid-chromatographic methods with postcolumn fluorescence detection using 5-sulfo-8-quinolinol were applied to the chemical speciation of aluminum in soil-extract samples. The addition of an appropriate amount of F-to the postcolumn reagent solution makes it possible to eliminate the interference of F-in a sample with A13+ detection. The reliability of this method was evaluated by a computer-assisted equilibrium calculation for aluminum species and ICP atomic emission spectrometry. Considerable parts of water-soluble A13+ (the A13+ fraction extracted into distilled water) in both sedimentary and granitoid soil samples were found to be complexed with organic substances. On the other hand, exchangeable A13+ (the A13+ fraction extracted into 1 mol dm-3 KCl) in granitoid soil samples was mostly free A13+

A K+ doped glass slab optical waveguide (SOWG) was coated with octadecylsilane (ODS) to separate and concentrate analytes onto the SOWG with hydrophobic interaction between analytes and ODS. As an absorption detector of flow analysis, the ODS–SOWG detector was almost insensitive to a blue dye (bromothymol blue) which is not adsorbed to the surface of the SOWG. On the other hand, it was highly sensitive to another blue dye of coomassie brilliant blue G-25O (CBB) which is firmly adsorbed onto the SOWG surface.