Increasing the trapping mass range to m/z = 10 ~9 - A major step toward high resolution mass analysis of intact RNA, DNA and viruses(Review)

摘要

This work demonstrates sampling of singly charged particles up to 200 nm in diameter at atmospheric pressure into vacuum and trapping large numbers(>10 ~6) at a point in front of the end cap electrode of a linear quadrupole ion guide/trap for on-demand injection into the acceleration region of a time-of-flight mass spectrometer in a well-collimated ion packet. This procedure was shown to yield trapping efficiencies that ranged from 4 to 5% for 10 nm diameter urea particles(～400 kDa) to 1% for 200 nm urea particles(～3 × 10 ~9 Da). Analysis of the inlet optimization procedure suggests that the inlet can be adapted to sample and trap beyond the 200 nm range. Review of the most likely places for ion loss in the sampling process suggests that the sampling and trapping efficiencies can be improved well beyond the 4-5% shown. Moreover, it suggests that sampling of smaller than 10 nm ions could achieve efficiencies in the 10s of percent range thereby suggesting new levels of sensitivity can be achieved for small ions(<200 kDa). Finally, demonstration of trapping large numbers of 200 nm(3 × 10 ~9 Da) ions for on-demand ejection in well collimated temporally discrete ion packets is a prelude to resolved mass analysis in that range.