Polyacrylamide gradient gel-filled capillaries with low detection background

Abstract A method has been explored for the production of low background polyacrylamide gradient gel-filled capillaries. The main idea is to prepare the capillaries by filling them with short steps of gelling solutions, including a long section of buffer for detection. This method is demonstrated to be practicable by scanning the filled capillaries. Smooth gradients can be formed at a step-length of 1.5 cm if the relevant capillaries are filled with solutions in a step-down order. By using this method, the desired capillaries were prepared with a success rate of >90% and gradient position error of ±0.62 mm. As shown by capillary gradient gel electrophoresis, this new type of capillary can be used for fast and efficient separation of polyaspartate and murein oligosaccharides (from E. coli ). They also allow the use of any available UV wavelength for high detection sensitivity. The unlabelled oligosaccharides at a total concentration of 1 mg ml −1 were directly detected at 200 nm.