Discrete micro-volume suspension injection to microwave induced plasma for simultaneous determination of cadmium and lead pre-concentrated on multiwalled carbon nanotubes in optical emission spectrometry

Abstract

A discrete sample introduction system (DSIS) for the direct micro-volume nanomaterials (NMs) suspension injection has been developed toward the simultaneous determination of Cd and Pb pre-concentrated (by dispersive micro solid-phase extraction (DMSPE)) on oxidized multiwalled carbon nanotubes (MWCNTs) to microwave induced plasma optical emission spectrometry (DMSPE-DSIS-MIP OES). On-axis low-volume spray chambers with flow focusing micro nebulizer (continues mode) and v-groove type pneumatic nebulizer (discontinues mode) for microliter-volume suspension introduction were tested.A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. Minimum dead volume, high nebulization and suspension transport efficiency were obtained by using miniaturized spray chamber/v-groove pneumatic nebulizer interface for 10 μL suspension injection in discontinues mode (at 0.5 mL min−1 pump speed).Analytical performance of DMSPE-DSIS-MIP OES method was characterized by determination of the limits of detection (0.7 and 0.1 ng mL−1 for Cd and Pb, respectively) and precision ranged from 6% to 8%. Quantitative data obtained for water reference materials (ERM-CA011b and SRM 1643e) were in good agreement, according to the t-test, for a confidence level of 95%, with the corresponding reference values, proving the potential of this analysis system for trace analysis via MIP OES. The proposed method had been successfully applied for the determination of Cd and Pb in water real samples.