RP-HPLC technique to separate lead, cadmium and mercury Ions by using ion-selective column modifier anchored C18 silica monolithic supports

In this work we demonstrate a highly efficient reversed-phase high-performance liquid chromatography (RP-HPLC) technique for the rapid and sequential analysis of toxic metal ions namely, Pb²⁺, Cd²⁺ and Hg²⁺. An indigenously synthesized 1,2-bis (2-hydroxy benzyl) phenylenediimine (BHBP) was used as the column modifier (ion-selective ligand) that was anchored on the C18 silica monolithic support (RP 18e 100 x 4.6 mm) by dynamic modification process to interact with the metal ion species in order to render desired resolutions. Optimum mobile phase was found to be 0.01 M tartaric acid (pH 4.0), which was employed at a flow rate of 1 mL/min in isocratic elution mode. The separated metal ions were subjected to in-situ post-column derivatization process using a metallo-chromogenic agent namely, 4-(2-pyridylazo) resorcinol and were monitored by UV-Visible detection system at 520 nm (λmax). The paramount chromatographic parameters such as the amount of column modifier, choice of mobile phase, flow rate of eluent and post-column reagent were optimized to obtain faster and well-resolved chromatographic peaks. All the targeted metal ions were separated within seven minutes of analysis time under controlled experimental conditions. The method offered excellent linearity, accuracy, limits of detection and quantification values. The obtained limits were found to be 0.060, 0.075 and 0.060 mg/L for Pb²⁺, Cd²⁺ and Hg²⁺ respectively. The method was selective for the targeted metal ions amidst other transition and post-transitions matrix components with an average recovery value of 99.82% (RSD ≤1.73%). (author)