A NEW USE OF THE KBR PRESSED-PELLET TECHNIQUE IN QUANTITATIVE INFRARED-SPECTROSCOPY

A new technique for the quantitative determination of ions by infrared spectroscopy is proposed, based on matrix isolation in pressed pellets of potassium bromide or other alkali halides. High specificity and low detection limits of this technique are the consequence of unusually sharp vibrational bands of matrix-isolated ions. The usefulness of the method is illustrated by the determination of nanomole amounts of nitrate ions in water. Under suitably adjusted conditions, the incorporation of nitrate in KBr matrices is complete and direct quantitation is feasible. Alternatively, an isotopic ion, such as (NO3-)-N-15, may be used as an internal standard. The extent of applicability of the method to ions other than the nitrate is discussed.