Highly alkaline electrolyte for single-stranded DNA separations by electrophoresis in bare silica capillaries

A new, highly denaturing electrolyte system based on a solution containing 0.01 M NaOH, 0.0015 M Na2B4O5(OH)(4) and a replaceable polymer sieving medi um was designed for the separation of single-stranded DNA fragments in bare fused-silica capillaries. Extreme denaturing power, together with the opti mized composition of the electrolyte, allows for a separation efficiency as high as 2 300 000 height equivalents to a theoretical plate per meter. Sam ple denaturation in alkaline solutions provides single-stranded DNA fragmen ts without any intra- or intermolecular interactions at room temperature. T heir electrophoretic mobilities were found to be twice those of fragments d enatured by dimethylformamide or HCl. This can be interpreted in terms of a n increased effective charge on the DNA molecules. The surprisingly weak el ectroosmosis (6.10(-10) m(2) V-1 s(-1)) of polymer solutions at pH 12 or hi gher is considered to be the result of the dissolution of the silica capill ary wall. A highly viscous thin layer of dissolved silica probably causes a shift of the slipping plane further away from the wall to the lower value of the zeta potential. Applications of the electrolyte in clinical diagnost ics demonstrate its remarkable properties. (C) 1999 Elsevier Science B.V. A ll rights reserved.