Development of an ion trap / linear time‐of‐flight mass spectrometer with electrospray ionization for micro‐column liquid chromatography detection

Abstract

AbstractA linear time‐of‐flight (TOF) mass spectrometer equipped with a quadrupole ion trap for ion storage was developed for mass analysis of ions generated by electrospray ionization (ESI). With this technique, the continuous ion beam from the ESI source is collimated by a set of focusing lenses into the ion trap where the ions are accumulated for a predetermined period of time. Extraction of the ions into the flight tube of the TOF mass spectrometer is achieved by applying a short duration voltage pulse to the exit endcap of the ion trap. The extraction frequency is variable, but is typically set at 10 Hz. It was shown that with a linear TOF mass spectrometer, mass resolution in the range of 600–950 can be routinely obtained. It was also demonstrated that a complete mass spectrum of bradykinin can be obtained with a direct injection of 75 fmol, or 0.5 μL of 150 nM of sample solution. Buffer gas pressure and the energy of the ions entering the ion trap, were found to be the key parameters in obtaining this sensitivity and resolution. In addition, the ESI ion trap/TOF system was developed and applied for microcolumn liquid chromatography detection of a simple protein mixture. © 1995 John Wiley & Sons, Inc.