A spot test for nitrite and nitrate detection by color band length and number of colored zebra-bands formed in a mini-column

Abstract

A detecting tube for nitrite and nitrate monitoring was developed as a spot test. The detecting tube was prepared by packing of poly(vinyl chloride) (PVC) particles coated with a quaternary ammonium salt into a mini-column. A nitrite solution was treated with sulfanilic acid and 1-naphthol; the resultant colored solution was drawn into the detecting tube by suction with a syringe, and a color band was formed in the tube. The color band length (CBL) corresponded to the nitrite concentration. Nitrate was also detected; after reduction with zinc. The nitrite and nitrate content of domestic wastewater samples was successfully detected by this method over the range of 0.5–45.3 mg-N L⁻¹ as nitrogen concentration. Another type of detecting tube was prepared by alternately packing adsorbent and uncoated PVC particles in a mini-column. Colored zebra-bands were formed in this column, and the nitrite concentration was detected by counting the number of colored zebra-bands. Nitrite and nitrate concentrations in actual wastewater samples were detected more easily by this method, although the accuracy was somewhat lower than that obtained with the CBL method.