Magnetic nano-adsorbent integrated with lab-on-valve system for trace analysis of multiple heavy metals

Abstract

A novel system for trace analysis of multiple heavy metals was developed wherein we have integrated a magnetic nano-adsorbent with a lab-on-valve system and coupled this to an inductively coupled plasma mass spectrometer. The magnetic nano-adsorbent was prepared by surface modification of iron-based magnetic nanoparticles with polyacrylic acid (MNPs-PAA). The MNPs-PAA possessing the superparamagnetic nature of MNPs could be controllably immobilized in PTFE tubing by an external magnetic force. The high surface density of PAA (3.30 × 10¹¹ molecules cm⁻²) on MNPs-PAA significantly reduced the amounts of adsorbent needed for adsorption of heavy metals (Mn²⁺, Co²⁺, Cu²⁺, Zn²⁺, and Pb²⁺). A detection limit of 0.04–0.06 µg L⁻¹ (except 0.6 µg L⁻¹ for Cu²⁺ and Zn²⁺), a precision smaller than 4% (RSD, n = 3), and a linear range of 0.5–50 µg L⁻¹ were obtained by directly injecting an aliquot of 20 µL fortified standard solution analyzed at 5 min per sample. The accuracy was evaluated by analyzing certified reference materials of SRM 2670a (trace elements in urine, low level) and CASS-2 (nearshore seawater reference material for trace metals). Good agreement between the measured and certified values demonstrated that the system is useful for trace analysis of multiple heavy metals in environmental and biological aqueous samples. The potential of integrating functionalized nano-materials to improve the performance of existing analytical systems as an alternative approach to green analytical chemistry is foreseen.