Abstract

A vertical cyclonic spray chamber/Nafion membrane-based desolvation system was used to eliminate the nitric acid interference in inductively coupled plasma atomic emission spectroscopy (ICP-AES). Three different matrices were studied: plain water and solutions containing 0.9 and 3.6 mol l⁻¹ of nitric acid. The liquid flow rate ranged between 20 and 600 µl min⁻¹. The cyclonic spray chamber was heated at 100 °C and the membrane at 60 °C, using air as dryer gas. The new desolvation system was robust since it accepted a nitric acid concentration change up to 3.6 mol l⁻¹ without a change in the emission signal, regardless of the element and line. Hence, elements in these matrices could be calibrated with standards prepared with de-ionized water. In order to test the plasma excitation conditions, the Cr II 267.716 nm to Cr I 357.869 nm line intensity ratio was measured for each combination of desolvation system and matrix. Standard configurations of desolvation systems were also evaluated, and the nitric acid depressive effect could only be eliminated when working at a high spray chamber temperature and/or low liquid flow.