Simultaneous determination of alcohols including diols and triols by HPLC with ultraviolet detection based on the formation of a copper(II) complex

We developed a reversed‐phase high‐performance liquid chromatography method with ultraviolet detection using on‐line complexation with Cu(II) ion for analysis of five alcohols including diols and triol (methanol, ethanol, 1,2‐propanediol, 1,3‐propanediol, and glycerol). The Cu(II) ion concentration in the mobile phase had a great influence on the peak areas of these alcohols, but not on their retention times. Column temperature (25−40°C) and pH of the mobile phase did not affect the separation of analytes. The optimum separation conditions were determined as 5 mM CuSO₄, 3 mM H₂SO₄, and 3 mM NaOH at 30°C. The ratio of the peak areas for three alcohols (methanol, 1,2‐propanediol, and glycerol) was in good agreement with that calculated from the obtained stability constants, molar absorption coefficients for the 1:1 Cu(II) complexes with the three alcohols, and the injected molar quantities. This fact strongly suggests that the observed high‐performance liquid chromatography signals resulted from formation of the 1:1 Cu(II)–alcohol complexes. Using the proposed method, these five alcohols in spirit, liquid for electronic cigarette, mouthwash, and nail enamel remover samples were successfully analyzed with only a simple pretreatment.