An RP-HPLC-UV Method for the Determination of Inorganic Mercury (II) via Sulfur-Donor Ligand Complexation and Ion-Pair Retention

Tahir Bakhsh, Nazhifa Jacinda Maheswari Abidin, Hermin Sulistyarti, Ani Mulyasuryani

Abstract

Mercury contamination in artisanal and small-scale gold mining regions requires accessible analytical methods, yet established techniques demand dedicated atomic spectrometry instrumentation. This study developed a reversed-phase HPLC-UV method for inorganic mercury(II) based on sulfur-donor ligand complexation and ion-pair retention on a conventional C18 column. Thiocyanate and L-cysteine were evaluated using tetrabutylammonium hydroxide (TBAH) as the ion-pairing reagent. Ultraviolet spectra recorded within the linear response range of the instrument placed the Hg-SCN absorption maximum at 240 nm, and detection was performed at 245 nm. A 1:16 Hg(II): SCN⁻ molar ratio and a final mobile-phase TBAH concentration of 8 mM (acetonitrile 70%, methanol 20%, aqueous TBAH 10% v/v) produced a dominant chromatographic peak. Against an experimentally measured void time of 2.70 min, retention changed regime rather than increasing progressively: the peak eluted before the void volume at 0.5 and 2 mM TBAH (k′ = -0.36) and was retained at 8 mM (k′ = +0.42). Calibration over 0.125-0.500 mM (25.1-100.3 mg/L), using seven independently prepared levels in triplicate, gave R² = 0.9929, an LOD of 0.033 mM (6.5 mg/L) and an LOQ of 0.109 mM (21.8 mg/L), the LOQ lying below the lowest calibration level. Retention-time and peak-area repeatability were 0.80% and 1.96% RSD, and mean recovery from spiked reagent water was 93.8%.  Specificity and matrix effects were not assessed. The validated range lies four orders of magnitude above drinking-water guideline values, so the method is intended as a preliminary procedure for concentrated process and waste streams rather than for environmental monitoring or mercury speciation

Keywords

Complexation; ion-pair RP-HPLC-UV; mercury(II); tetrabutylammonium hydroxide; thiocyanate

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References

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DOI: https://doi.org/10.20961/jkpk.v11i2.122567

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