Masuyoshi Yamada

Development of a portable mass spectrometer characterized by discontinuous sample gas introduction, a low-pressure dielectric barrier discharge ionization source, and a vacuumed headspace technique.

The present study has attempted to downscale a mass spectrometer in order to make it portable and enable onsite analysis with it. The development of a small mass spectrometer required the use of a compact pump whose displacement was small, decreasing the sensitivity of that spectrometer. To get high sensitivity with a small mass spectrometer, we have integrated novel techniques: a highly sensitive ionization source and efficient extraction of sample vapor. The low-pressure dielectric barrier discharge ionization (LP-DBDI) source made it possible to increase the conductance between the source and the mass analyzer, compared with ambient ionization sources, enhancing the efficiency of the ion transfer from the ionization source to the mass analyzer. We have also developed a vacuumed headspace method efficiently transporting the sample vapor to the ionization source. The sensitivity was further enhanced by also using a discontinuous sample gas introduction technique. A prototype portable mass spectrometer using those novel techniques was found to be sensitive enough to detect 0.1 ppm methamphetamine, 1 ppm amphetamine, 1 ppm 3,4-methylenedioxymethamphetamine, and 10 ppm cocaine in liquid.

Analysis of volatile metabolites from cultured bacteria by gas chromatography/atmospheric pressure chemical ionization–mass spectrometry

An analytical system using gas chromatography/atmospheric pressure chemical ionization-mass spectrometry (GC/APCI-MS) was suitably set up for the analysis of volatile metabolites from cultured bacteria. The developed system was proved to have high sensitivity: the detection limit for a standard sample of indole was 17 pg (33 ppt (parts per trillion) for 100 mL gas sample). The system was extensively applied to rapid analysis of volatile metabolites from different bacteria: Escherichia coli, Streptococcus pneumoniae, and two strains of Staphylococcus aureus. A total of 156 metabolite peaks were peculiar to one of the species among 163 metabolite peaks found for all of the bacteria. The experimental results suggest that the GC/APCI-MS has the potential to distinguish bacterial pathogens rapidly by detecting bacterial volatile metabolites.

Probe Heating Method for the Analysis of Solid Samples Using a Portable Mass Spectrometer

We previously reported on the development of a portable mass spectrometer for the onsite screening of illicit drugs, but our previous sampling system could only be used for liquid samples. In this study, we report on an attempt to develop a probe heating method that also permits solid samples to be analyzed using a portable mass spectrometer. An aluminum rod is used as the sampling probe. The powdered sample is affixed to the sampling probe or a droplet of sample solution is placed on the tip of the probe and dried. The probe is then placed on a heater to vaporize the sample. The vapor is then introduced into the portable mass spectrometer and analyzed. With the heater temperature set to 130°C, the developed system detected 1 ng of methamphetamine, 1 ng of amphetamine, 3 ng of 3,4-methylenedioxymethamphetamine, 1 ng of 3,4-methylenedioxyamphetamine, and 0.3 ng of cocaine. Even from mixtures consisting of clove powder and methamphetamine powder, methamphetamine ions were detected by tandem mass spectrometry. The developed probe heating method provides a simple method for the analysis of solid samples. A portable mass spectrometer incorporating this method would thus be useful for the onsite screening of illicit drugs.