IMPACT OF MEMBRANE DESOLVATION ON THE EFFECTS OF SODIUM ON RESPONSE IN INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY WITH ULTRASONIC SAMPLE INTRODUCTION

This report compares the influence of sodium on response with ICP-AES for copper, cadmium, lead and cobalt with ultrasonic sample introducti on in the presence and absence of a microporous membrane desolvation ( MMD). Comparisons are reported at viewing positions of 8, 14, and 20 m m above the load coil, for injector gas flow rates of 0, 70, 0.85 and 1.00 l min(-1), and at sodium concentrations ranging from 0.00 to 0.08 M Na. Blank emission intensities were depressed in the presence of so dium regardless of the operating condition(s), Depressions in the blan k emission intensities were greater without the MMD, but were less tha n 20%, The magnitude of depression in the blank emission intensities d id not vary significantly among the analyte lines or with the viewing position, The impact of sodium on signal intensities with and without the MMD was greater than the impact on the blank emission intensities, with changes approaching 150%, At the lower viewing positions, signal enhancement in the presence of sodium was common and the degree of en hancement was greater with the MMD, Response changes with respect to s odium concentration were also different with and without the MMD low i n the plasma. Higher in the plasma, element-to-element variation occur red in the nature of the impact of sodium, For signals that were enhan ced, the degree of enhancement was generally greater with the MMD, but when signals were depressed, there was no correlation to the presence or absence of the MMD. In contrast to the lower viewing position, hig her in the plasma response changes with respect to the sodium concentr ation were similar. These results suggest that although the plasma is physically different with and without the MMD, the MMD does not alter the mechanism(s) by which sodium impacts response.