Optimization of volatile organic compound sensitivity of Vocus PTR-ToF-MS for quantifying disinfection byproducts



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Recent advances in volatile organic compound (VOC) measurement techniques have led to the release of the Vocus 2R PTR-ToF, which offers real-time measurements of over 1500 compounds. The Vocus 2R PTR-ToF mass spectrometer offers world-leading sensitivity and mass resolution for the detection of VOCs in multiple ionization modes, but to maximize its capabilities it is important to adjust its operational parameters to reach the highest sensitivities for VOCs of interest. Here, a known mixture of 17 compounds was measured by the Vocus PTR-ToF at a constant flow rate as parameters of the Vocus, such as the reactor temperature, pressure, and voltage were ramped individually. Two ionization modes, H₃O⁺ and NH₄⁺, were used and sensitivities were optimized for each through evaluation of the ramping routine. As a case study to apply the optimized parameters, bleach and hydrogen peroxide were introduced to an environmental chamber via two methods: (a) spraying from a bottle onto a tabletop and (b) vaporizing into a mist using a humidifier within the chamber. The Vocus PTR-ToF detects compounds from many functional groups over a wide range of masses and its time resolution allows for differentiation of compounds emitted directly from the disinfectant spraying from byproducts resulting from indoor chemistry.


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