Herein, a flow injection analysis (FIA) was established for the spectrophotometric determination of total dissolved nitrogen (TDN) in natural waters. An on-line ultraviolet digester was used for sample digestion, and a nontoxic and soluble reductant, vanadium chloride (VCl3), was for the first time used in flow injection method for TDN determination. The digestion mode, reagent concentration, and influence of organic matter were investigated. The experimental results revealed a detection limit of 0.04 mgN L-1 and linearity of up to 3.0 mgN L-1. Recovery from natural water samples was between 87.0 and 104.4%. The accuracy of the method was ensured by using national certified reference materials of total nitrogen GSB 07-3168-2014 (batch NO. 203261 and 203262), and satisfactory results were achieved. The proposed method was used to the determination of TDN in natural water samples, and results obtained were similar to those provided by the autoclave alkaline persulfate digestion and copperized cadmium column reduction method. The results obtained herein showed that the proposed method had a high potential for field or monitoring application.

Total dissolved nitrogen; Vanadium reduction; Ultraviolet digestion; Flow injection analysis; Spectrophotometry

Third Institute of Oceanography State Oceanic Administration; Guilin University of Electronic Technology