Correction of spectral interferences arising from cn emission in

Abstract

Introduction of sample stream air into argon inductively coupled plasma permits continuous monitoring of hazardous air pollutant metals in combustion flue gases. In addition to entrained particulates, various molecular components of flue gas are in the plasma. These species, and reaction products thereof, such as CN species, also undergo excitation resulting in complex emission spectra of appreciable intensity. Serious spectral interference arises for several metal elements, from molecular emission bands associated with the stable CN radical, and other poly-atomic species, such as NO. Failure to account for these interferences can significantly degrade accuracy of monitoring particularly at low metal concentrations in the flue gas. This invention corrects spectral interferences arising from airborne molecular species in the argon plasma even when the magnitudes of spectral interferences encountered during the analysis of airborne metals in flue gases, are of such considerable magnitudes that, if not directly accounted for, would otherwise compromise the quality of measurements of the airborne metals. This method measures and corrects spectral interferences attributed to CN and NO that affect on-line detection of hazardous air pollutant metals. The method incorporates conventional spectrometer hardware and existing instrument software to achieve effective real-time correction of these interferences.