Increased MS sensitivity with ion funnel focusing. Technology developments such as the ion funnel greatly increase MS instrument sensitivity by re-focusing all ions through narrow interfaces necessary to maintain the high vacuum required for MS measurements. Two ion funnels are depicted here. The first funnel on the left is a conventional ion funnel that focuses the continuous beam from two capillaries through a narrow inlet. The second funnel (right) is a trapping ion funnel used to trap and pulse ions for ion mobility spectrometry (IMS) experiments. ESI, electrospray ionization.