Development of an analytical method using ultra-micro flow

Analytical methods using continuous ultra-micro flow were developed for the purpose of downsizing the amounts of wastewater discharged from analytical measurements. The sampling of environmental water was also suggested. All tubes of the sampling and measuring apparatus were a fused silica capillary of 0.25 mm inner diameter at a flow rate of about 1μl/min; this method was applied for COD as well as nitrate and nitrite ions in environmental water. A continuous monitoring apparatus for COD as well as nitrate and nitrite ions based on Japanese Industrial Standard methods were constructed. In the monitoring apparatus for COD, the sample water and acidic a potassium permanganate solution, a silver nitrate solution was pumped with a syringe pump at a total flow rate of 1.6 μl/min. Nitrate and nitrite ions were also simultaneously determined spectrophotometrically on the basis of a diazotization-coupling reaction. Nitrate ion was reduced to nitrite ion with a cupperized cadmium micro-column prior to the reactions. These methods were successfully applied to continuous monitoring of COD as well as nitrate and nitrite ions in laboratory sewage. The amount of wastewater produced by a continuous measurement was under 1l per year.