Broad-band ion accumulation with an internal source MALDI-FTICR-MS.

A new method is described which allows a broad mass range of ions from multiple MALDI events to be accumulated in an FIICR analyzer cell prior to detection. Signal intensity and signal-to-noise ratio are observed to grow in direct proportion to the number of laser shots, providing a substantial improvement to the analysis of low-level samples compared to more commonly used signal-averaging methods. In addition, calibrant ions desorbed from a separate sample spot can be added to the analyzer cell after an analyte population has been accumulated, providing an internal mass standard without the necessity of mixing calibrant and analyte. This method provides excellent mass accuracy by eliminating mass errors due to space charge effects.