Apparatus and method to improve the filtering action of a quadrupole mass filter by reducing a precursor fault caused by an asymmetric electrical field between a pair of opposing electrode rods in a y-axis of the quadrupole mass filter. The request may be based at least in part on the at least one information insert. Let L=|S2n\u2212S2n\u22122|, C=|S2n+2\u2212S2n|, and R=|S2n+4\u2212S2n+2|. 1 percent of a quaternary ammonium compound; and between 0. Each comb-teeth part has thereon, at a tip portion thereof, at least one of the contact plugs.