Direct Biological Sample Analyses by Laserspray Ionization Miniature Mass Spectrometry

With improved performances, miniature mass spectrometers are becoming suitable for more practical applications. At the same time, the coupling of an approximate ionization source is essential in terms of minimizing sample preparation and broadening the range of samples that could be analyzed. In this study, an atmospheric pressure laserspray ionization (AP-LSI) source was coupled with our home developed miniature ion trap mass spectrometer. The whole system is compact in size, and biological samples could be directly analyzed with minimum sample preparation. Direct detections of peptides, proteins, drugs in whole blood, and urine could be achieved with high sensitivity. The analyses of tissue sections were demonstrated, and different regions in a tissue section could be differentiated based on their lipid profiles. Results suggest that the coupling of AP-LSI with miniature mass spectrometer is a powerful technique, which could potentially benefit target molecule analysis in biological and medical applications

Mass Selective Ion Transfer and Accumulation in Ion Trap Arrays

The concept and method for mass selective ion transfer and accumulation within quadrupole ion trap arrays have been demonstrated. Proof-of-concept experiments have been performed on two sets of ion trap arrays: (1) a linear ion trap with axial ion ejection plus a linear ion trap with radial ion ejection; (2) a linear ion trap with axial ion ejection plus a linear ion trap with axial ion ejection. In both sets of ion trap arrays, ions trapped in the first ion trap could be mass selectively transferred and accumulated into the second ion trap, while keeping other ions reserved in the first ion trap. Different operating modes have been implemented and tested, including transferring all ions, ions within a selected mass range, ions with a mass-to-charge ratio of 1, and randomly selected ions. Unit mass resolution for ion transfer and ∼90% ion transfer efficiency has been achieved. A new tandem mass spectrometry scheme for analyzing multiple precursor ions in a single sample injection has been demonstrated, which would improve instrument duty cycle and sample utilization rate (especially for very limited samples), potentially facilitate applications like single cell analyses, and improve electron transfer dissociation efficiency