SIMPLE MULTIPOINT DETECTION METHOD FOR HIGH-PERFORMANCE CAPILLARY ELECTROPHORESIS

A simple device for multi-point detection was designed to record the course of an analysis by high-performance capillary electrophoresis (HPCE). Determinations of mobilities and relative peak areas can be performed with an accuracy higher than that obtained with conventional HPCE equipment. Two principles were utilized (in both instances the polyimide coating is removed at the detection points desired). In one approach, the fused-silica tubing, following a first recording, is moved "backwards" to a new position for a second recording, and so on. The other approach utilizes a piece of tubing which, after a straight stretch, is curved into loops; the first monitoring takes place as the solutes leave the straight stretch, the second when they leave the first loop, the third when they leave the second loop, and so on (the straight stretch can, of course, be replaced with a loop). The technique is illustrated with an electrophoretic analysis in free solution of DNA and peptides. Interestingly, lambda-DNA is separated into several extremely narrow zones. By using multi-point detection it could be demonstrated that the appearance of the DNA pattern changed in an unexpected, discontinuous way during a run.