Sequential injection analysis of nitrate ions using a microfluidic polymer chip with an embedded ion-selective electrode

A sequential injection analysis (SIA) system for the determination of NO₃^- ions using a microfluidic polymer chip with an embedded NO₃^- ion-selective electrode (NO₃ ^--ISE) as a detector was developed. Under the optimal flow conditions of the SIA system, the NO₃^--ISE showed a good linear relationship between peak heights and logarithmic concentrations of NO ₃^- ions with a Nernstian slope of 57.1 mV per decade in a concentration range from 1.0 × 10^-5 to 1.0 × 10 ^-1 mol dm^-3. Sample throughput of the present system for the determination of NO₃^- ions was ca. 12 samples per h. The proposed SIA system was applied to the determination of the level of NO ₃^- ions in environmental water samples, such as tap water, well water and river water.