Chip-based capillary electrophoresis with an electrodeless nanospray interface

A sheathless and electrodeless nanospray interface has been used to interfa ce a polycarbonate capillary electrophoresis (CE) chip to a mass spectromet er (MS), The chip was made of two Rat polycarbonate plates which were bolte d together, Channels were imprinted in one of the plates with metal wires, using a hydraulic press. A short tapered capillary connected to the chip wa s used as the nanospray emitter. The advantage of this electrodeless interf ace is that it was not necessary to apply a electrospray voltage to the chi p or the nanospray emitter. Instead, the CE voltage already applied to the buffer compartment on the chip, to drive the electrophoresis, was used to g enerate the spray also. A low conductivity buffer of 1.25 mmol/L ammonium acetate in 80% methanol w as used to obtain a large electric field across the buffer channel. The per formance of the device was evaluated by analyzing a mixture of three beta-a gonists Relative standard deviation (RSD) values obtained were between 4.8 and 5,0%, A sample concentration of 40 nmol/L resulted in a signal-to-noise ratio of 2 to 5 for the different components. Compared to a conventional C E analysis in a fused silica capillary with UV detection, only a minor loss of resolution was observed, which can he attributed to the design of the c hip. Copyright (C) 2000 John Whey & Sons, Ltd.