Continuous preconcentration system for nitrate ions using anionic reverse osmosis tubes coupled to an ion chromatograph

A continuous preconcentration system for nitrate ions was developed using cation exchange tubing made from Nafion perfluorosulfonic acid membrane. This method is based on ion exclusion effects and reverse osmosis phenomena. The system was evaluated by connecting it to an ion chromatograph. The concentration ratios could be increased by raising the pressures between the two sides of the cation exchange tubing. Twenty-fold concentration of nitrate ion was achieved when the pump pressure was 20 x 10(5) Pa. The relative standard deviations of the preconcentration ratio at four different pump pressures, 5, 10, 15 and 20 x 10(5) Pa were 1.2-2.8% (n = 5).