Field determination of nitrate in seawater using a novel on-line coppered cadmium column: A comparison study with the vanadium reduction method

Nitrate is the main form of dissolved inorganic nitrogen, playing an important role in both marine biogeochemical research and water environment management. In this work, most commonly used coppered cadmium column was modified a novel on-line Cu/Cd with spiral structure coupled de-bubbling device syringe-type filter developed. With advantages convenience, portability, stability, high reduction efficiency, interference air bubbles could easily be avoided. Based on classic Griess reaction, simple reverse flow injection system custom-made cell established for field spectrophotometric determination nitrate seawater. The effects certain reaction parameters—including reagent concentration, rate, length column, salinity—were investigated, optimized, compared pure water, approximate 9% increase sensitivity seawater samples. This method exhibited detection limit 0.03 μmol/L, relative standard deviation 0.6%, working range 20 μmol/L before dilution. Compared to referred vanadium based same system, proposed showed significant including reproducibility. No difference observed between analytical sample results obtained by reference methods. Furthermore, validated first class National Certified Reference Materials successfully applied Wenling coastal (Zhejiang, China).