An optimised quadrupole mass spectrometer with a dual filter analyser for in-field chemical sniffing of volatile organic compounds

We report a novel portable 17 kg system based on a quadrupole mass spectrometer (QMS) with an electronic
power consumption of 24 W. The system can be used for the in-field identification of gases and
volatile/semivolatile organic compounds (VOCs/SVOCs). The mass analyser is a custom-made quadrupole
mass filter with a Brubaker pre-filter that gives a mass range of m/z 1–500. It is an upgrade of the previous
m/z 1–200 range triple filter analyser system. Analyser design was optimized using 3D numerical simulations
as a performance trade-off between single and triple filter designs while maintaining high sensitivity
and ease of integration. This also required enhanced design of the electronic control unit (ECU)
compared to the previous triple filter ECU designs with lower power consumption, size, weight and cost
of the overall system. Another major ECU improvement includes high stability of DC voltage control and
ultra-low RF drift, which is important for in-field applications that require stable mass peaks for reliable
quantitative analysis and continuous monitoring. Experimental results are presented for the perfluorotributylamine
(PFTBA) calibrant and acetone to assess the functionality of the instrument. Performance
comparison between the dual and triple filter quadrupole analysers has also been done. Mass spectra are
given for methyl benzoate (cocaine simulant), piperidine (phencyclidine simulant), cyclohexanone (C4
simulant) and 2-nitrotoluene (TNT simulant) to assess potential capability for the identification of threat
compounds. All spectral results show good correlation with the NIST library mass spectra with unit resolution
obtained for spectral peaks within a m/z 1–400 mass range.