Flow Injection Analysis with Spectrophotometry for Ammonium ion with 1-Naphthol and Dichloroisocyanurate

The proposed FIA is based on a modified Berthelot reaction of ammonium ion with 1-naphthol and dichloroisocyanurate to form an indophenol blue derivative. We study to improve the sensitivity of the modified Berthelot reaction, and propose the addition of acetone. The FIA consists of two line flow system. Reagent solution 1 is an alkaline (14.5 g L of NaOH) sodium dichloroisocyanurate (1.2 g L) solution containing of trisodium citrate dehydrate (4 g L). Reagent solution 1 plays a sample carrier role in the FIA. Reagent solution 2 is 1-napthol (24 g L) solution (water : acetone : ethanol = 4 : 1 : 5). The interference of foreign ions in the sample is studied and removed by the addition of the complexing reagent, such as citrate. A linear range of the FIA is 0 to 4.0 μg mL of ammonium ion. The relative standard deviation is 0.6% for 2.0 μg mL of ammonium ion (n = 10) and the detection limit is 0.013 μg mL of ammonium ion. The FIA is applied to environmental water samples, such as river, lake, and sea water.