A Microextraction Method Based on Ligandless Ion-Pair Formation for Measuring the Cadmium Cation in Real Samples by Flame Atomic Absorption Spectrometry

Abstract

A new, simple, and ligandless ion-pair microextraction method has been developed for preconcentration and determination of cadmium ion in saline solutions and food samples. This technique is based on using a double chain cationic surfactant called didodecyldimethylammonium bromide (DDAB) as an ion-pairing agent and extraction solvent combined with dispersive microextraction named supramolecule aggregate-based dispersive liquid-solid microextraction (SA-DLSME) prior to aspiration to flame atomic absorption spectrometer. The Cd2+ ion interacts with chloride ion in saline solution, and the resulting anionic complex is microextracted by cationic supramolecule aggregates of DDAB due to electrostatic interaction. This technique benefits the advantages of supramolecule aggregate properties and dispersive liquid-liquid microextraction technique without the use of any dispersing solvent. Phase separation behavior of DDAB and several effective parameters that have influence on extraction efficiency of cadmium ion such as pH, salt concentration, centrifugation time, and DDAB amount were thoroughly investigated and optimized. Under the optimized experimental conditions, the limit of detection (LOD) and linear range were 1.3 and 5–250 ng mL−1, respectively, with relative standard deviations (RSD) in the range of 3.1–4.3 for interday analysis and 4.5–5.5 for intraday tests at different concentrations of cadmium. The proposed method was successfully applied for the determination of cadmium ion in real samples, and its accuracy was confirmed by analysis of a certified reference material.