Characterization of bioparticles using a miniature cylindrical ion trap mass spectrometer operated at rough vacuum

Abstract

A miniature cylindrical ion trap mass spectrometer (CIT-MS) equipped with an inexpensive mechanical pump was constructed, and used to measure the masses of cells and microparticles generated by laser induced acoustic desorption ionization. Compared with a previous lab scale quadrupole ion trap mass spectrometer (QIT-MS), the novel miniature CIT-MS had smaller volume (the radius r₀ = 5 mm), simpler ion trap fabrication and overall instrument construction, required a lower trapping voltage, and reduced the weight, power and cost of the instrument. The CIT-MS was calibrated using standard polystyrene beads of 2.982 µm diameter. The CIT-MS was used to measure the total dry weight of human red blood cells (RBCs) from a healthy female adult (2.12 × 10¹³ Da) and a patient with anemia (1.35 × 10¹³ Da). The coefficient of variance (CV) for the healthy individual was 21% and that for the patient was 30.4%. The CIT-MS was also applied to guinea pig RBCs and the total dry weight was determined as 1.34 × 10¹³ Da with a CV of 37.9%. These measurements are consistent with previous QIT-MS measurements. The new miniaturized instrument has potential for applications in field-portable, biological and aerosol analysis.