Study on determination of iron, cobalt, nickel, copper, zinc and manganese in drinking water by solid-phase extraction and RP-HPLC with 2-(2-quinolinylazo)-5-diethylaminophenol as precolumn derivatizing reagent

Abstract

A new method for the determination of iron, cobalt, nickel, copper, zinc and manganese in drinking water by the reversed-phase high-performance liquid chromatography (RP-HPLC) with 2-(2-quinolinylazo)-5-diethylaminophenol (QADEAP) as precolumn derivatizing reagent was studied in this paper. The iron, cobalt, nickel, copper, zinc, and manganese ions react with QADEAP to form color chelates in the presence of cetyl trimethylammonium bromide (CTMAB) and acetic acid–sodium acetic buffer solution medium of pH 4.0. These chelates were enriched by solid-phase extraction with a Waters Nova-Pak C₁₈ cartridge and eluted the retained chelates from the cartridge with tetrahydrofuran (THF). The enrichment factor of 100 was achieved. Then the chelates were separated on a Waters Nova-Pak C₁₈ column (3.9 × 150 mm, 5 µm) by gradient elution with methanol (containing 0.2% of acetic acid and 0.1% of CTMAB) and 0.05 mol L⁻¹ acetic acid-sodium acetic buffer solution (containing 0.1% of CTMAB) (pH 4.0) as mobile phase at a flow rate of 0.5 ml min⁻¹, and monitored with a photodiode array detector from 450∼700 nm. The detection limits (S/N = 3) of iron, cobalt, nickel, copper, zinc and manganese are 0.8, 1.1, 0.9, 1.1, 1.5 and 2.0 ng L⁻¹, respectively, in the original sample. This method can be applied to determination at the µg L⁻¹ level of iron, cobalt, nickel, copper, zinc and manganese in drinking water with good results.