Sequential determination of multi-nutrient elements in natural water samples with a reverse flow injection system

An integrated system was developed for automatic and sequential determination of NO2-, NO3-, PO43-, Fe2+, Fe3+ and Mn2+ in natural waters based on reverse flow injection analysis combined with spectrophotometric detection. The system operation was controlled by a single chip microcomputer and laboratory-programmed software written in LabVIEW. The experimental parameters for each nutrient element analysis were optimized based on a univariate experimental design, and interferences from common ions were evaluated. The upper limits of the linear range (along with detection limit, mu mol L-1) of the proposed method was 20 (0.03), 200 (0.7), 12 (0.3), 5 (0.03), 5 (0.03), 9 (0.2) mu mol L-1, for NO2-, NO3-, PO43-, Fe2+, Fe3+ and Mn2+, respectively. The relative standard deviations were below 5% (n=9-13) and the recoveries varied from 88.0 +/- 1.0% to 104.5 +/- 1.0% for spiked water samples. The sample throughput'was about 20 h(-1). This system has been successfully applied for the determination of multi-nutrient elements in different kinds of water samples and showed good agreement with reference methods (slope 1.0260 +/- 0.0043, R-2=0.9991, n=50).