Complex mixture analysis by two-dimensional mass spectrometry using a miniature ion trap

Quadrupole ion trap mass spectrometers are robust instruments that can perform tandem mass spectrometry (MS/MS) while being operated under moderate vacuum conditions. These features make quadrupole ion traps an attractive option as miniature mass spectrometers, particularly because the sensitivity and selectivity gained from employing MS/MS does not decrease with reduced instrument size. Recent developments in scan methodology have allowed quadrupole ion traps to be used to perform two-dimensional MS/MS (2D MS/MS) experiments which identify all precursor ions and their dissociation products. This study describes the implementation of this single scan in a miniature mass spectrometer where sample amount is limited, and time is prioritized. Remarkably, the miniature instrument 2D MS/MS experiment demonstrated greater sensitivity than a benchtop ion trap mass spectrometer utilizing the 2D MS/MS scan. Even more notably, the 2D MS/MS experiment performed using the miniature instrument achieved higher mass resolution than the benchtop instrument in both precursor and product ion dimensions. The miniature instrument's performance was tested on mixtures of drugs of abuse in the presence of a matrix as well as on a mixture of phospholipids.