Interference Effects from Easily Ionizable Elements in Flame AES and ICP‐OES: A Proposed Simplified Rate Model Based on Collisional Charge Transfer Between Analyte and Interferent Species

Abstract

The effects of excess Na and K on K and Mg atom line emission in the air‐acetylene flame and of excess Li and K on Ca, Mg, and Sr atom and ion lines in inductively coupled plasma spectroscopy were studied using emission signal ratios, I′/I as probes, where I′ and I are the emission readings in the presence and absence of the interferent respectively. The I′/I plots as a function of analyte concentration in the test solution for the ICP experiments were similar to those obtained for the flame experiments in the analytical range 0–10 mg/L. A simplified rate model based on analyte excitation via charge transfer between analyte ions and activated interferent atoms is proposed to account for the emission signal enhancement observed at low analyte concentrations (<1 mg/L) for both ICP‐AES and flame atomic emission spectroscopy (AES). Data are presented showing good agreement between experimental E′ calibration curves and theoretical E′ calibration curves computed using the simplified rate model.

Keywords:

• Calibration curve
• collisional charge transfer
• easily ionizable element
• flame AES
• ICP‐AES
• simplified rate model

Acknowledgments

This work was supported by a grant from the Research Board of the University of Zimbabwe (UZ). The courtesy of the director and staff of the Institute of Mining Research of UZ, Mr. Kahwai and Mr. Ansari, and that of the management and staff of Bindura Nickel Corporation in availing us the use of their ICP spectrophotometers is gratefully acknowledged.