Analysis of nanomolar concentrations of phosphate in seawater with Liquid Waveguide after Mg （OH）2 coprecipitation

Phosphorous is an essential nutrient used by plants and animals for growth and energy transport. Phosphate cycling studies are important in understanding biological processes, and phosphate analyses are a standard part of the biogeochemists＇ toolbox. However, these standard techniques fail to be applied to low concentration environments due to a lack of sensitivity. Such low concentration environments include the central gyres such as the North Pacific and North Atlantic subtropical gyres and northeastern Mediterranean gyres where phosphate concentrations average less than 50 nM. In this study, a method was developed to analyze DIP using Liquid Waveguide after Mg （OH）2 coprecipitation. This method uses magnesium （Mg） in seawater sample as a carrier to coprecipitate phosphate. This method has a very low reagent blank because only sodium （Na） hydroxide and 1% HCl are used and these reagents can be easily purified. The simplicity of this method also minimizes the potential for phosphate contamination during sample handling. The aim of this study is to develop a technique for analysis of phosphate in seawater, which is simple, accurate and precise. We used Liquid Waveguide to guarantee accuracy and detect phosphate at levels comparable to the lowest seen in seawater.