Improved high‐performance liquid chromatography of vitamin E vitamers on normal‐phase columns

A method is described for improving column stability and reproducibility for analysis of vitamin E vitamers on normal‐phase high‐performance liquid chromatography columns with isooctane/ethyl acetate/acetic acid/2,2‐dimethoxypropane (98.5:0.9:0.85:0.1) mobile phase. Acetic acid in the mobile phase reduced retention times of vitamin E vitamer and increased column stability. A small concentration of 2,2‐dimethoxypropane, which reacts with water to form acetone and methanol, reduced the need for column regeneration and stabilized retention times.