Quantification of Pb2+ using thiourea functionalised metal-organic frameworks in the MEPS method followed by graphite furnace atomic absorption spectroscopy analysis

Abstract

ABSTRACT This study aimed to develop a novel method for extracting trace amounts of Pb2+ in water samples using thiourea-functionalised MOF-199 in microextraction by packed sorbent (MEPS). The primary objectives were synthesising and characterising the sorbent, optimising extraction parameters, and evaluating the method’s performance in real-world applications. The prepared sorbent was characterised using FTIR, FESEM, and EDX. Various extraction efficiency parameters were optimised, including sample pH, sorbent amount, loading cycles, eluent cycles, sample volume, and eluent type and volume. Under optimal conditions, the proposed method demonstrated excellent analytical performance with a low limit of detection (0.005 µg L−1), limit of quantification (0.058 µg L−1), high extraction efficiency (93.8%), good linearity (0.06–40 µg L−1), and satisfactory precision (RSD = 0.41%, n = 10, CPb = 20 µg L−1). Notably, thiourea-functionalised MOF-199 exhibited significantly enhanced Pb2+ extraction ability compared to untreated MOF-199, with a saturated adsorption capacity of 99.58 mg g−1 at pH = 6. The method’s applicability was successfully demonstrated by extracting Pb2+ from three fish species’ river water, vegetables, and muscle tissues, achieving satisfactory recoveries of 99.42–100.4%. The novelty of this work lies in developing a highly efficient and sensitive MEPS method using thiourea-functionalised MOF-199 for Pb2+ extraction. Thiourea preferentially coordinates with the central Cu of the MOF-199 through its C=S functional group, leaving the nitrogen atoms free to interact with Pb2+ ions. This innovative approach offers a promising solution for trace Pb2+ analysis in complex environmental and biological matrices.