Comparison of continuous flow analysis and ion chromatography for determinations of nitrate, nitrite and phosphate ions in seawater and development of related seawater certified reference materials

Abstract

Determinations of three nutrients (nitrate, nitrite and phosphate ions) in seawater were investigated by continuous ow analysis (CFA) based on colorimetry and ion chromatography (IC). The accuracies of those methods were examined by discussing their uncertainties. While CFA is popular in this eld, its comparison with IC was reported for the rst time and contributed to an increase in the reliability of the analytical results. Finally, the investigation led to the development of three kinds of seawater certi ed reference materials (CRMs) of the National Metrology Institute of Japan (NMIJ) (NMIJ CRM 7601-a, 7602-a and 7603-a) for which the property values of nutrients including dissolved silica were given. The details of the development are described in the present paper.