Development of a high-performance MALDI-TOF mass spectrometer utilizing a spiral ion trajectory

A novel MALDI-TOF mass spectrometer that utilizes a spiral ion trajectory was developed. In this mass spectrometer, the ions sequentially passed through four toroidal electrostatic sectors and revolved along a figure-eight-shaped orbit on a particular projection plane. Each toroidal electrostatic sector had eight stories, and during multiple revolutions, the ion trajectory shifted perpendicular to the projection plane in every cycle, thereby generating a spiral trajectory. The flight path length of one cycle was 2.1 m; therefore, when the ions completed eight cycles, the total flight path length was 17 m. By adopting an ion optical system that had a flight path length five times longer than that in the commonly used reflectron ion optical system, the mass dependence on the mass resolving power was reduced, while improving the mass accuracy of the mass measurements. The basic performance of the system was tested by using standard peptides or the tryptic digest of bovine serum albumin. A mass resolving power of 80,000 (full width at half maximum) was achieved at m/z = 2564 (ACTH18-39). An improved mass accuracy less than 2 ppm was realized over a wide m/z range of 500 to 3000 by correction using one or two internal standard substances.