A laser-induced rf plasma (LIRFP) ion source was developed to ionize submicrometer-sized particles for the first time. The LIRFP ion source can increase the charge of those particles to several thousand charges via charge exchange reactions so that those particles can be trapped and analyzed with a charge detection quadrupole ion trap-mass spectrometer (CD QIT-MS). Different reagent gases for charge exchange reaction were investigated, viz. argon, nitrogen, oxygen, methane, helium, krypton, xenon, argon/methane (with ratios of 10:1 and 2:1), argon/nitrogen (with a ratio of 1:1), nitrogen/oxygen (10:1), krypton/methane (10:1), and air. The average charge of 0.75 μm polystyrene particles could reach 1631 using an argon/methane mixture with a ratio of ∼10:1. The average charges for freeze-dried Escherichia coli EC11303, Escherichia coli strain W, and Staphylococcus aureus were 842, 1112, and 971, respectively, with a mass-to-charge ratio (m/z) range from 10 7 to 10 8 ; and the average masses were 3.5 × 10 10 Da, 6.0 × 10 10 Da, and 5.6 × 10 10 Da, respectively. The average mass and charge of the vaccinia virus were ∼9.1 × 10 9 Da and ∼708 with a m/z of ∼10 7 . This LIRFP CD QIT-MS method was rapid with only 20 min for each sample measurement.

Polyhydroxyalkanoate (PHA) is one of the biocompatible and biodegradable plastics that can be produced and accumulated as granules inside microorganisms. In this study, a new approach to rapidly quantify a short-chain-length PHA, polyhydroxybutyrate (PHB), produced from genetically engineered Escherichia coli containing phaCAB is presented. The mass of each bacterial cell was measured using a laser-induced radio frequency (rf) plasma charge detection quadrupole ion trap mass spectrometer (LIRFP CD QIT-MS), and then, the PHB contents were determined by calculating the change in cellular mass. The quantitative results showed that the PHB contents measured by LIRFP CD QIT-MS were consistent with those by reference analysis, gas chromatography (GC). The PHB content of each bacterial sample can be obtained within 20 min from sampling using LIRFP CD QIT-MS while GC analysis takes 2 days. In addition, LIRFP CD QIT-MS does not use any hazardous chemicals in cellular mass quantification as compared to GC. This indicates that LIRFP CD QIT-MS has potential in routine monitoring of PHB production.