A New Spectrophotometric Method for Measuring COD of Seawater

This research studied a new spectrophotometric method for measuring the chemical oxygen demand (COD) of seawater. In this method, the COD was measured using a spectrophotometer instead of titrating with sodium thiosulphate. The measuring wavelength was selected to be 470 nm, and the COD of three standard glucose solutions (COD=0.5, 1.5 and 2.5 mgL−1, respectively) and two seawater samples (from the South Yellow Sea and Jiaozhou Bay) were measured using the spectrophotometric method and titrimetric method respectively. The results showed that the spectrophotometric method was somewhat better than the titrimetric method. The relative standard deviation (RSD) of the spectrophotometric method was less than 2.7%, and the recovery of seawater samples ranged from 96.3% to 103.8%. In addition, the spectrophotometric method has other advantages such as expeditiousness, operation simplicity, analysis automatization,etc. Therefore the spectrophotometric method can be used to measure the COD of seawater with satisfactory results.