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The online monitoring of hydrogen sulfide (H 2 S) presents a critical advancement for environmental protection and public health, yet existing methodologies struggle to achieve on-site, on-line and highly sensitive detection in atmospheric conditions. This study introduces a novel approach employing ozone-enhanced photoionization ion mobility spectrometry (IMS) in conjunction with a time-resolved dynamic diluter (TRDD) for the efficacious identification of H 2 S within environments of high humidity, such as sewers. This method ingeniously addresses the challenge of distinguishing H 2 S in the presence of water vapor through a dual strategy of ozone oxidization pretreatment and TRDD injection. The strategic placement of ozone within the drift region significantly amplifies the sensitivity of the IMS detection, showcasing the method's superior sensitivity, stability, and humidity interference resilience. Notably, this technique achieves a detection limit for H 2 S at an impressive 2.5 parts per billion (ppb), maintaining a consistent relative standard deviation (RSD) of 2.5 % over three consecutive days. Furthermore, the approach effectively mitigates the effects of moisture, maintaining an RSD of 3.0 % despite a relative humidity (RH) increase from 22 % to 95 %. Applied to the on-site measurement of H 2 S in sewer systems, the method demonstrated all the aforementioned performance characteristics, marking it a promising way of high humidity environment H 2 S monitoring. [Display omitted] • H 2 S was sensitively detected with ozone-enhanced ion mobility spectrometry. • The limit of detection of 2.5 ppb for H 2 S was achieved. • Moisture effect was avoided using time-resolved dynamic dilution inlet method. • Stability with relative standard deviation as low as 0.59 % was achieved. [ABSTRACT FROM AUTHOR]

Exhaled hydrogen cyanide (HCN) has been extensively investigated as a promising biomarker of the presence of Pseudomonas aeruginosa in the airways of patients with cystic fibrosis (CF) disease. Its concentration profile for exhalation can provide useful information for medical disease diagnosis and therapeutic procedures. However, the complexity of breath gas, like high humidity, carbon dioxide (CO 2) and trace organic compounds, usually leads to quantitative error, poor selectivity and sensitivity for HCN with some of existing analytical techniques. In this work, acetone-assisted negative photoionization (AANP) based on a vacuum ultraviolet (VUV) lamp with a time-of- flight mass spectrometer (AANP-TOFMS) was firstly proposed for online measurement of trace HCN in human breath. In-source collision-induced dissociation (CID) was adopted for sensitivity improvement and the signal response of the characteristic ion CN− (m/z 26) was improved by about 24-fold. For accurate and reliable analysis of the exhaled HCN, matrix influences in the human breath including humidity and CO 2 were investigated, respectively. A Nafion tube was used for online dehumidification of breath samples. Matrix-adapted calibration in the concentration range of 0.5–50 ppbv with satisfactory dynamic linearity and repeatability was obtained. The limit of quantitation (LOQ) for HCN at 0.5 ppbv was achieved in the presence of 100% relative humidity and 4% CO 2. Finally, the method was successfully applied for online determination of human mouth- and nose-exhaled HCN, and the nose-exhaled HCN were proved to be reliable for assessing systemic HCN levels for individuals. The results are encouraging and highlight the potential of AANP-TOFMS with in-source CID as a selective, accurate, sensitive and noninvasive technique for determination of the exhaled HCN for CF clinical diagnosis and HCN poisoning assessment. Image 1 • Acetone-assisted negative photoionization-TOFMS was firstly proposed for online measurement of trace HCN in human breath. • In-source collision-induced dissociation (CID) was adopted for sensitivity improvement. • Matrix influences in the human breath including humidity and CO 2 were investigated for accurate and reliable analysis. • Satisfactory selectivity, sensitivity and repeatability was obtained with this method. [ABSTRACT FROM AUTHOR]

Humidity as a major issue affects the quantitative performance of ion mobility spectrometry (IMS) in field applications. According to the kinetic equations of ion-molecular reaction, the intensity ratio of the product ion peak (PIP) over the reactant ion peak (RIP) is proposed as a quantitative factor to correct real-time humidity variation. By coupling this method with a unidirectional anisole-assisted photoionization IMS, direct breath-by-breath measurement of intraoperative propofol was achieved for the first time, which provided more clinical information for studying the anesthetics pharmacokinetics. Although the signal intensities of the RIP and the propofol PIP both declined along with the increase of humidity, the intensity ratio of Propofol/(RIP + Propofol) kept almost constant in a wide relative humidity range of 0%–98%, enabling direct quantitation of exhaled propofol with varying humidity. Furthermore, interfering ion peaks resulted from the high concentration humidity and anesthetics in single exhalation were eliminated during the balanced anesthesia as the exhaled sample was diluted by the unidirectional gas flow scheme. As a demonstration, breath-by-breath variation profiles of propofol were obtained via monitoring end-tidal propofol concentration of intraoperative anesthetized patients (n = 7). The analyses were quantitative, corrected for humidity in real-time, without measuring the humidity content of each breath sample during operation, which show potential for the quantitative analysis of other high humidity samples. Image 1 • IMS sensor for breath-by-breath measurement of intraoperative propofol was developed. • Real-time humidity correction for precisely quantifying exhaled propofol was proposed. • Interference of exhaled humidity and anesthetic agents was reduced by flow dilution. [ABSTRACT FROM AUTHOR]