Selective Determination of Mercury Ion in River Water by Solvent Extraction with 4,6‐Dimethyl‐2‐Mercaptopyrimidine Followed by Reversed‐Phase HPLC

Abstract

A selective determination method for mercury (Hg) ion in river water has been developed by solvent extraction, followed by reversed‐phase HPLC with photometric detection. The Hg(II) ion was quantitatively extracted into chloroform over the pH range of 2.9 to 5.4 as 4,6‐dimethyl‐2‐mercaptopyrimidine (DMMP) chelate. Job's method indicated that the Hg‐DMMP chelate composition was Hg(DMMP)2. The extracted Hg‐DMMP chelate was then separated on an ODS column with an eluent of methanol/water/0.1 M DMMP (60∶40∶0.25, v/v) and detected at 255 nm. The correlation coefficients of the calibration curves obtained with 5 mL Hg standards were more than 0.999 over the range of 0.2 µg/mL (ppm) to 10 ppm. The detection limit of the Hg ion in 5 mL water was estimated as 0.02 ppm, by a signal to noise ratio of 3. The recoveries with a spiked river water sample for 0.5 and 5 ppm Hg ion (N=5) were 100.9±1.2% and 100.1±0.8%, respectively. Effects of foreign ions on the determination of 0.5 ppm Hg ion were investigated with 57 metal ions. Almost none of the ions interfered except for Ag(I), Au(III), and Cu(II).