On-line method for overcoming phosphate interference in the automated cadmium reduction method for the determination of nitrate

Abstract

Phosphate in the millimolar concentration range was found to interfere with the reduction of nitrate to nitrite in the Technicon automated determination of nitrate. The phosphate interference was dependent on the amount of phosphate to which the cadmium reduction column was exposed. The interference was not permanent and could be removed by washing the column. The Technicon method was modified to provide an on-line means of removing phosphate (up to 50 mM), by precipitation with calcium chloride, prior to the samples entering the reduction column.