SENSITIVE SPECTROPHOTOMETRIC DETECTION OF SILICIC-ACID IN PURE WATER WITH SLAB OPTICAL WAVE-GUIDE ABSORPTION DETECTOR

Blue silicomolybdate anion was adsorbed onto a glass slab optical wave guide (SOWG) surface as an ion associate with cetyltrimethylammonium c ation and was detected with the SOWG absorption detector using a semic onductor laser (780 nm) as a light source. The sensitivity of the SOWG method for 2 cm(3) of a pure water sample was ca. 20 times higher tha n that of conventional spectrophotometry at 3 ppb Si level, and the de tection limit was ca.0.2 ppb Si (S/N=3).