Selective and Sensitive Determination of Mercury(II) Ions in River Water by an Automatic HPLC System Combined with On-Line Column Enrichment as 2-Mercaptopyrimidine Chelate

Abstract

A selective and sensitive determination method for mercury (Hg) ions in river water by reversed phase high performance liquid chromatography (HPLC) has been developed. Two mL of water sample containing Hg(II) ions was put into a 4 mL sample tube. To the sample tube, 500 µL of 2 mol/L (M) acetate buffer solution (pH 4.5), and 50 µL of 0.01 M 2-mercaptopyrimidine (MP) were added to form a neutral Hg chelate. The Hg chelate subsequently became preconcentrated in a reversed phase mini column. By switching the valve, the Hg chelate was separated and detected at 255 nm. These processes occur automatically, except for the addition of water samples, buffer, and MP solutions. The correlation coefficients of the calibration curves obtained with 2 mL of mercury standard were more than 0.999 over the range of 20 ng/mL (ppb) to 10 µg/mL (ppm). The detection limit of Hg ions in 2 mL solution was 1.6 ppb, which corresponded to 3 times the standard deviation (N = 10) of the blank peak area. Effects of foreign ions on the determination of 0.2 ppm Hg were investigated with 57 metal ions. Almost none of the ions interfered except for Au(III), Pd(II), Ag(I), and Co(II) ions. The recoveries with spiked river water samples for 5, 0.5, and 0.05 Hg ion (N = 7) were 99.7 ± 0.4%, 100.3 ± 0.3%, and 100.7 ± 0.7%, respectively.