Flow injection analysis method for determination of total dissolved nitrogen in natural waters using on-line ultraviolet digestion and vanadium chloride reduction

•VCl3 was used as a reductant in flow injection method for TDN determination.•An on-line ultraviolet digester was proposed for sample digestion.•The proposed approach provides similar results with a well-known reference method.•The proposed analytic method is suitable for TDN determination in natural waters.