Suspension Nebulization Analysis of Clays by Inductively Coupled Plasma‐Atomic Emission Spectroscopy

Abstract

AbstractUse of suspension nebulization for elemental analysis of clays by inductively coupled plasma‐atomic emission spectroscopy (ICP‐AES) was evaluated to ascertain the effects of particle size and various experimental parameters on total recoveries. To do so, specimens of Grundite illite and Georgia kaolinite no. 3 were fractionated by centrifugation to prepare samples of the <0.2‐, 0.2‐ to 2‐, 2‐ to 10‐, and 10‐ to 45‐µm size fractions. Portions of these samples were dispersed in 1 M HNO3 or 0.1 M NaCl and analyzed by ICP‐AES using suspension nebulization. Other portions of the samples were digested with HF and analyzed by ICP‐AES using solution nebulization. Total recoveries were determined by comparing the sum of all oxides for the suspension‐ and solution‐nebulization analyses. Total recoveries ranged from 2 to 100% depending on particle size of the samples, design of the spray chamber, observation height, carrier Ar pressure, sample nebulization rate, and method of sample preparation. Incident power of the plasma did not substantially affect total recoveries. The highest total recoveries were obtained by sonicating samples for 10 min at 80 W in 0.1 M NaCl, and by maximizing sample nebulization rate (2.6 mL min−1), minimizing carrier Ar pressure (1.52 mPa), and using a conical spray chamber for the analyses. For the <0.2‐ and 0.2‐ to 2‐µm size fractions, these conditions yielded reproducible results with total recoveries >90%. Total recoveries for the 2‐ to 10‐ and 10‐ and 45‐µm size fractions, however, never exceeded 70 and 24%, respectively. Therefore, suspension nebulization is not recommended for use with samples containing particles larger than 2 µm. Use of suspension nebulization with ICP‐AES, however, is a rapid and reliable method for performing multielement analyses of clay (<2‐µm) samples.