Infrared spectrometric determination of nitrate, nitrite and ammonium ions by means of matrix isolation in pressed alkali metal halide pellets

Abstract

A technique is proposed for the determination of ions by infrared spectrometry, based on ion exchange and matrix isolation in alkali metal halide pressed pellets. The sharpness of the vibrational bans of many of the matrix-isolated ions ensures high specificity, good quantification and low detection limits. The extent of applicability of this technique is surveyed and the experimental procedures that are required are presented. The application of the method to the determination of nanomole amounts of nitrate, nitrite and ammonium ions in water is described. Under suitably adjusted conditions, the incorporation of these ions in KBr and CsCl is complete and direct quantification is feasible. Quantification is also possible by the use of 15N-labeled internal standards. Nitrate and nitrite give much narrower bands in KBr than in CsCl whereas the opposite is true for ammonium ions. In general, optimum determinations may require different alkali metal halide matrices for different ions. The technique should be adaptable to the determination of many other polyatomic ions.