Gradient elution of hydroxyacetophenones by supercritical fluid chromatography with electrochemical detection

Linear gradient elution supercritical fluid chromatography with electrochemical detection was developed using hydroxyacetophenones as analytes. Separation was carried out with a diol column (4.6 mm id × 250 mm length, 5 μm) as a stationary phase and a mixture of supercritical carbon dioxide and methanol as a mobile phase, where the ratio of carbon dioxide and methanol was changed from 99:1 (v/v) to 60:40 (v/v). For the electrochemical detection, methanol containing 1.0 mol L^-1 ammonium acetate was used as a supporting electrolyte solution and + 1.2 V was applied to the electrochemical cell. We compared the performance of the present method to isocratic elution supercritical fluid chromatography, and the repeatability, linearity, and detection capability all showed better analytical parameters in the gradient elution. As such, we found that gradient elution supercritical fluid chromatography can achieve the faster separation and save resources compared to isocratic elution. Thus, the present method may contribute to the development of green analytical methods.