Wheat varietal identification by capillary electrophoresis: An inter-laboratory comparison of methods

Capillary electrophoresis (CE) is a rapid automated method for wheat protein analysis It is sensitive, reproducible, and gives high resolution separation of gliadins, differentiating most genotypes. Optimal CE conditions have not yet been established, however, nor methods compared between laboratories. We therefore analysed gliadins from several varieties by two methods in two laboratories using comparable CE systems. A commercial 0.1 mol/L phosphate buffer, pH 2.5, containing a linear hydrophilic polymer, was used with uncoated 27 cm silica capillaries (20 cm from inlet to detector) of 50 and 20 mu m i.d. Separations with 50 mu m capillaries were performed at 7 kV and required 30-40 min; those with 20 mu m capillaries were performed at 22 kV, and separations took about 10 min. In each laboratory, both methods gave excellent separations with comparable selectivity and resolution. For some analyses (especially those using 50 mu m capillaries), however, elution times and operating currents varied with different batches of commercial buffers, giving unacceptable reproducibility. Thus, while CE is a useful alternative to slab gel electrophoresis or high performance liquid chromatography for wheat varietal identification, CE buffer compositions must be carefully controlled to ensure acceptable reproducibility.