Determination of Copper Ion in River Water by Solvent Extraction with 2-Mercaptobenzothiazole Followed by Reversed Phase HPLC

Abstract

A determination method for Copper (Cu) ion in river water has been developed by reversed phase HPLC combined with solvent extraction. The Cu(II) ion was quantitatively extracted into benzene from a weak acidic solution as 2-mercaptobenzothiazole (MBT) chelate. The extracted Cu-MBT chelate was then separated on a C₁₈ column with an eluent of methanol/water (88:12, v/v) and detected at 275 nm. The correlation coefficients of the calibration curves obtained with 5 mL Cu standards were more than 0.999 over the range of 0.01 to 10 µg/mL (ppm). The detection limit of the Cu ion in 5 mL water was 3 ng/mL, which corresponded to 3 times the standard deviation (N = 8) of the blank peak area. Effects of foreign ions on the method were investigated with 0.4 ppm Cu standard and 57 metal ions. Almost none of the ions interfered except for Au(III), Pt(IV), V(V), and Zr(IV) ions. Recoveries with a spiked river water sample for 5 and 0.5 ppm Cu ion were 99.9 ± 0.5% and 99.8 ± 0.8%, respectively (N = 6).

Keywords:

• 2-Mercaptobenzothiazole
• Copper (Cu) ion
• High performance liquid chromatography (HPLC)
• Photometric detection
• River water
• Solvent extraction

Notes

y: peak area (mV sec), x: concentration of Cu ion (ppm).

^a Standard deviation.

^b Relative standard deviation.

^c The results were obtained on other days.

Note. The tolerance limit of the foreign ion concentration was taken as the value that caused an error of less than 10% in the recovery of Cu ion (0.4 ppm).