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.
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