Performance improvements for a miniature quadrupole with a micromachined mass filter

Conventional quadrupole mass filters are usually constructed from metallic rods of length 50-225 mm and diameters 5-15 mm. In this study the conventio nal arrangement has been replaced with a micromachined mass filter made fro m silicon with Au metallised specially drawn glass fibres of length 30 mm a nd diameter 0.5 mm. This assembly was mounted on a vacuum flange with a VG ANAVAC ion source and a Faraday plate collector. Conventional electronics w ere adapted to run at 6 MHz and mass spectra in the range 0-50 amu were obt ained. The results indicate a linear mass scale with 5-10% valley separatio n between O-2/N-2 peaks and a best resolution at 10% peak height of 2.7 amu at mass 40. It is believed that the recent improvements in performance are due to optimisation of the electronics coupled with refinements in the mic romachining technique employed. (C) 1999 Elsevier Science Ltd. All rights r eserved.