RESUMO
A cadmium column reduction-azo dyes spectrophotometric method based on micro sequential injection lab-on-valve was established for the determination of total nitrogen in seawater. The experimental parameters were optimized, and the interference experiment was carried out. The results showed that the interference of the main components and salinity in sea water could be eliminated by using a series of standard solution prepared by national standard seawater with certain salinity. The concentration of total nitrogen in seawater was linear with the absorbance in the range of 0 . 03-1 . 00 mg/L with a correlation coefficient of 0. 9993. When determining the national standard seawater at nitrogen concentration of 0. 20 mg/L, the relative standard deviation (RSD) was 4. 9%, the detection limit was 0. 010 mg/L, and the recoveries were 99. 5%-101 . 1%. There were not significance differences between the results of this method and national standard method in the t-test analysis. The method is suitable for the determination of total nitrogen in seawater.