the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Sep 2025
All-in-One: Validation and Versatile Applications of a Novel Chemical Ionization Mass Spectrometer for Simultaneous Measurements of Volatile Organic and Inorganic Compounds
Abstract. Volatile organic compounds (VOCs) and volatile inorganic compounds (VICs) are crucial players in atmospheric chemistry, and their coexistence in industrial environments, particularly semiconductor manufacturing, presents significant obstacles to production yields. The simultaneous and high-time-resolution measurements of both VOCs and VICs from a single platform have long been an analytical Achilles’ heel, often requiring compromises in sensitivity or selectivity for certain compound classes. This study introduces and comprehensively evaluates a novel Vocus B Chemical Ionization Time-of-Flight Mass Spectrometer (CI-TOF-MS), an improved “all-in-one” solution that overcomes this challenge by rapidly switching between reagent ions and polarities. Laboratory-based calibrations for a suite of VOCs and VICs, including ammonia (NH3) and various amines, demonstrated excellent linearity (R2 > 0.99) and high sensitivity. An inter-comparison experiment for NH3 with an established cavity ring-down spectroscopy analyzer (Picarro G2103) showed strong overall agreement in tracking major pollution events and diurnal trends. We demonstrate the instrument’s versatility through three distinct applications: (1) stationary in-situ monitoring in urban Nanjing, which captured complex pollution dynamics and identified a previously overlooked industrial solvent hotspot; (2) mobile laboratory deployment along the Nanjing-Hefei corridor, which successfully mapped pollution gradients and attributed sources in real-time; and (3) real-time monitoring of Airborne Molecular Contaminants from a Front Opening Unified Pod, simulating its utility for yield improvement in semiconductor fabrication. This work establishes the Vocus B as a versatile tool, offering a unified and efficient approach to elucidate the complex chemical interactions in both atmospheric science and industrial process control.
Competing interests: Yuanjian Yang is a member of the editorial board of Atmospheric Measurement Techniques.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2025-4515', Anonymous Referee #1, 07 Oct 2025
- AC1: 'Reply on RC1', Tianhao Ding, 10 Dec 2025
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RC2: 'Comment on egusphere-2025-4515', Anonymous Referee #2, 09 Oct 2025
The manuscript presents a detailed and comprehensive evaluation of the Vocus B CIMS for simultaneous measurement of volatile organic compounds (VOCs) and inorganic gaseous species. The study is gernally well written and I recommend it for publication after addressing the following comments:
One of the main advantages of the Vocus B is its ability to measure a wide range of VOCs using different reagent ions. While this study emphasizes the synchronous measurement of VOCs and inorganic species, primarily ammonia, it would be beneficial to include mass spectra for the three reagent ion modes. A discussion on the advantages of measuring VOCs with the Vocus B compared to previous versions of the instrument would be important. Specifically, it is challenging to assess whether the Vocus B offers a clear advantage in measuring ammonia when compared to a more compact and relatively lower-cost alternative, such as the Picarro instrument.
Additionally, a detail that seems to be missing is the cycling process between the three ionization modes. How long does the instrument operate in each mode? Could the authors clarify the time allocated to each mode in the cycling process? Furthermore, the calibration of VOCs was conducted using the benzene reagent ion mode. It would be helpful to know if the authors have also conducted calibration for VOCs using the other two reagent ion modes (Figure 1). This would allow for a comparison of results across the different modes and provide insight into the consistency of measurements.
The term "volatile inorganic compounds" may not be entirely appropriate in this context. I suggest using "inorganic gaseous species" or another more specific term, especially since the focus in this study is primarily on ammonia.
Citation: https://doi.org/10.5194/egusphere-2025-4515-RC2 - AC2: 'Reply on RC2', Tianhao Ding, 10 Dec 2025
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- 1
Volatile organic compounds (VOCs) and volatile inorganic compounds (VICs) are important target analytes, both in an environmental context and industrial process control. The simultaneous analysis of both compound groups with a high temporal resolution and sensitivity is still challenging. To overcome this challenge, the authors introduce the novel Vocus B Chemical Ionization Time-of-Flight Mass Spectrometer. This instrument can serve as an “all-in-one” solution, quasi-simultaneously targeting both compound groups by rapidly switching between multiple reagent ions and polarities.
The manuscript is well-structured and easy to understand. It is also written in clear, appropriate English. The authors provide a comprehensive description of the Vocus B’s performance in controlled laboratory tests and three relevant real-world applications. The use cases are well-chosen and presented, demonstrating the device’s versatility and usefulness in air pollution research and industrial applications. The results are presented logically and comprehensively, and the advantages over other established measuring devices are clearly highlighted. I therefore favor publishing this manuscript in Atmospheric Measurement Techniques after minor revisions.
Minor comments:
Line 157: “…, and various aromatics (chlorobenzene, styrene, etc.)” - Styrene and other aromatics are shown in Figure S1. The only (hetero)aromatics in Figure 1 are chlorobenzene and pyridine.
Figure 1: I suggest adding the plots for toluene and/or o-xylene (representing the BTEX compound group) and α-pinene (representing a major forest VOC) from Figure S1 in the main manuscript. There appears to be sufficient space for three additional plots in the current layout. This would emphasize the relevance and suitability of the proposed instrument for environmental research and enhance transparency by including examples with lower, yet still satisfactory linearity.
Lines 196 – 201: Since the calibration curves for ethylamine and dimethylamine are quite distinct, how would you calculate and report the sum of C2-amines? And how does this improve the quantification of an unknown mixture of both analytes?
Figure 4: Were the other VOCs also measured with the Vocus Elf PTR-TOF-MS? If so, did you also observe good agreement with the Vocus B data?
Figure 6: As you stated in lines 173-175, the calibration of highly corrosive, acidic gases is technically challenging. How robust are the results for HF, HCl and SO2 in this use case? Especially the signals for SO2 and HCl seem to show a comparably high fluctuation or noise.
Technical comments:
Line 56: “… (PTR-MS) are highly effective …”
Lines 158-168: I suggest to add the reference to Figure S1 here, since the calibration curves of aromatics are presented there.