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

Abstract

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.

Miniature and Fieldable Mass Spectrometers: Recent Advances

“…Non-ambient ionization techniques that have been utilized with mini MS systems include external ionization sources such as conventional electrospray ionization, atmospheric pressure chemical ionization, 57–59 extractive electrospray, 60 synchronized discharge, 61 and electrosonic spray ionization 62 as well as internal ionization sources that include electron ionization, 63 dielectric barrier discharge ionization, 51 and glow discharge electron impact. 64 However, the non-ambient nature of these methods along with the added complexity in some cases may limit their use in future experiments, particularly in the field.…”

“…51 In the latter instrument, a diaphragm pump is used to pump down the sample container to transfer vapors through a pinch valve into the ion source. An AC voltage is applied to a dielectric, resulting in ionization of analytes.…”

Development of a Miniature Mass Spectrometer and an Automated Detector for Sampling Explosive Materials

“…19,20) The study was intended to produce a mass spectrometer that was sufficiently compact that it would be portable and be used in an onsite analysis. The development of a small mass spectrometer required the use of a compact pump whose displacement was small, thus decreasing the sensitivity of that spectrometer.…”

Microplasma Ionization of Volatile Organics for Improving Air/Water Monitoring Systems On-Board the International Space Station

“…Steady growth in the development of microplasmas and other low power plasma for analytical chemistry applications has been seen in the recent literature [14,15], the driving force being the potential for developing small, low power devices with reduced operational cost and increased fieldability [16,17], with many focused on coupling to portable low resource MS instrumentation [18][19][20]. Microplasma-based miniature ion sources operated under ambient sampling/ionization conditions have the additional advantages of high sample throughput and simplicity, enabling direct analysis with little or no sample preparation [21,22].…”