The Mesoporous Porphyrinic Zirconium Metal-Organic Framework for Pipette-Tip Solid-Phase Extraction of Mercury from Fish Samples Followed by Cold Vapor Atomic Absorption Spectrometric Determination

Abstract

In this study, the highly stable mesoporous porphyrinic zirconium metal-organic framework, namely PCN-222/MOF-545 (Zr-MOF), was prepared and used for pipette-tip solid-phase extraction of Hg(II). As a high-capacity sorbent, 4 mg of the Zr-MOF was placed into a conventional pipette tip and used, for the first time, for the fast extraction and preconcentration of mercury ions. For desorption, 50 μL of 10% HCl was used by 15 repeated aspirating/dispensing cycles, and Hg ions in elusion were measured by a cold vapor atomic absorption spectrometer. Affecting parameters on extraction efficiency were studied, and optimum conditions were established as amount of sorbent 2 mg, pH was adjusted to 5.0, the eluting volume was 15 μL, and extraction was performed on 1.8 mL of the sample. The optimal number of aspirating/dispensing cycles for extraction and desorption of analytes was found to be 10 and 15 cycles, respectively. The limit of detection of the method was found to be 20 ng L−1 with a relative standard deviation of ≤3.1% (for seven replicate analyses of 20 μg L−1 of mercury). Adsorption capacity and enrichment factor were 35.5 mg g−1 and 120-fold, respectively. The proposed method was successfully applied for the determination of Hg(II) ions in fish samples.