Generation of multiple electrosprays using microfabricated emitter arrays for improved mass spectrometric sensitivity

Arrays of microelectrospray emitters were fabricated on polycarbonate, subs trates using a laser etching technique. Stable multielectrosprays were succ essfully generated in the liquid flow rate range relevant to mass spectrome tric applications, Comparison of electrosprays generated from the microfabr icated emitter array and conventional fused-silica capillaries showed simil ar spray characteristics and reliability. Higher total electrospray ion cur rents were observed as the number of electrosprays increased at a given tot al liquid flow rate. Consistent with the theoretical prediction, the total spray current at a constant total liquid flow rate was shown experimentally to be approximately proportional to the square root of the number of elect rosprays. It is further projected that when total flow rate is optimized th e maximum achievable total current will be proportional to the number of em itters. Evaluation of the multielectrospray device using a triple quadrupol e mass spectrometer showed a factor of 2-3 sensitivity enhancement for the spray numbers ranging from two to nine compared to a conventional single el ectrospray ionization source under the same operating conditions.