Reversed Phase Dispersive Liquid–Liquid Microextraction for Sensitive Ion Chromatographic Determination of Metal Cations in Sesame Oil

Abstract

Reversed-phase dispersive liquid–liquid microextraction (RP-DLLME) was proposed in the present work to separate and preconcentrate metal cations in sesame oil before their detection through ion chromatography-conductivity detection (IC-CDD). This method facilitates the direct extraction of cations like Na⁺, Pb²⁺, K⁺, Mg²⁺, and Ca²⁺ from oil specimens into an aqueous micro-drop to inject into the chromatography column. Four parameters were included in the process as the pH of water, volume of water and THF, and centrifugation time through a response surface technique. Five replicated analyses were performed under optimized circumstances (1.5 mL THF as a disperser and 60 μL water at pH 9 as an extraction solvent). Thus, recoveries of 110%, 108%, 107.2%, 104.2%, and 106.8% were displayed with respective standard deviations of 10.3, 9.8, 7.3, 9.7, and 6.7 for K⁺, Na⁺, Mg²⁺, Pb²⁺, and Ca²⁺. The detection limits (3σ) for the method were 0.007 μg mL⁻¹ for K⁺, 0.001 μg mL⁻¹ for Na⁺, 0.011 μg mL⁻¹ for Mg²⁺, 0.008 μg mL⁻¹ for Pb²⁺, and 0.009 μg mL⁻¹ for Ca²⁺. The method could successfully determine the existence of metal cations in four sesame oil specimens.