On-line MALDI-TOF MS using a continuous vacuum deposition interface

In this work, a new interface for continuous on-line MALDI-TOF MS is presen ted. The sample, mixed with a suitable matrix, was transported into the eva cuated source chamber of the mass spectrometer at liquid flow rates of 100- 400 nL/min, The liquid sample matrix was deposited on a rotating quartz whe el and transported to the repeller, where laser desorption took place. Rapi d evaporation of the solvent (water or methanol) on the surface of the whee l resulted in formation of a thin, similar to 50-mu m-wide, sample trace. S canning electron microscopic photographs of the vacuum-dried trace revealed the deposited material to consist of an amorphous film. Furthermore, sampl e uniformity along the trace, in conjunction with its narrow width, resulte d in excellent signal reproducibility, with detection limits in the attomol e range. The interface permitted the on-line coupling of microcolumn separa tion techniques with MALDI MS, as demonstrated in the capillary electrophor esis MALDI-TOF MS analysis of a 12-peptide mixture. The approach offers the potential for rapid separation and trace analysis of complex mixtures.