An automatic reserve flow injection method using vanadium (III) reduction for simultaneous determination of nitrite and nitrate in estuarine and coastal waters.

An automatic reserve flow injection method using vanadium (III) as a reducing agent for the simultaneous determination of nitrite and nitrate in estuarine and coastal waters was reported for the first time. Vanadium (III) chloride was used as an environmentally friendly substitute to toxic cadmium for reducing nitrate to nitrite. The experimental parameters were optimized based on a univariate experimental design. The salinity effect of estuarine and coastal waters was carefully investigated. Under the optimized conditions, the detection limit of the proposed method was 0.06 µmol L-1 and 0.13 µmol L-1, and the linearity was up to 20 µmol L-1 and 80 µmol L-1 for nitrite and nitrate detection, respectively. The relative standard deviations were below 1.5% (n = 7). The recovery of spiked estuarine and coastal water samples varied from 100.0 ± 2.5% to 107.5 ± 2.5% for nitrite and 90.7 ± 0.3% to 98.0 ± 1.0% for nitrate. The sample throughput was approximately 15 h-1. The analytical results obtained with the proposed method displayed good agreement with the classic copperized cadmium column reduction method. The automatic reserve flow injection method has been successfully applied to analyze the nitrite and nitrate in estuarine and coastal water samples.