title: Comparison of Hadamard transform and signal-averaged detection for microchannel electrophoresis.
abstract: A Hadamard transform (HT) detection method for microchip capillary electrophoresis with laser-induced fluorescence and a charge-coupled device (CCD) is described and compared to signal-averaged detection. A low-noise CCD camera is used to image a section of a separation channel where each camera pixel can be thought of as a unique detector. For signal averaging, electropherograms corresponding to individual pixels can be averaged for improved S/N. HT detection is performed on each pixel electropherogram to generate a contour plot electropherogram. The multiple injections required for HT provides an enhancement at the cost of longer times for the pseudorandom injection sequences. A short sample injection length of 0.25 s is used to reduce the overall analysis time and improve sensitivity compared to previously published results. An injection sequence is performed on the microchip that is based on a cyclic S-matrix of 513 elements that generates an 8-fold improvement in S/N compared to a single injection. This spatially resolved HT detection method is also capable of performing a multicomponent separation. Signal-averaged HT and single-injection data are compared to experimental HT and single-injection results. The unique capabilities of each method are described.
authors.affiliation: Department of Chemistry (M/C 111), University of Illinois at Chicago, 845 West Taylor Street, Room 4500, Chicago, Illinois 60607-7061, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: McReynolds
authors.forename: Scott A
authors.initials: SA
authors.lastname: Shippy