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UV photoionization (UV-PI) is a promising non-radioactive ionization method for ion mobility spectrometry (IMS). It could work at either direct photoionization mode or chemical ionization mode by adding photoionizable dopants, and thus its applications extend to a wide range of compound classes. This work is to present a comprehensive review on the development of UV-PI-IMS. It focuses on UV-PI's capabilities and how to use them fully. A summary discussion of the ionization processes in UV-PI would be presented first for understanding the fundamentals of UV-PI-IMS. Followed by descriptions of the technical configurations of UV-PI source in IMS. Improvements in the design of UV-PI source for achieving optimum results will be presented with references to examples. Further, a broad range of applications, including environmental contaminants analysis, trace explosives and chemical warfare agents detection, food safety and quality analysis, and clinical diagnosis, would be presented to demonstrated the analytical performance of UV-PI-IMS. In the conclusion, perspectives on areas of UV-PI technique which have the potential to be improved would be reasonably presented. Image 1 • UV photon driven ionization processes in UV-PI source were summarily interpreted. • Configurations of UV-PI source for IMS and their improvements were discussed. • Applications demonstrating the analytical performance of UV-PI-IMS were presented. • Perspectives on areas of UV-PI which need further improvements were proposed. [ABSTRACT FROM AUTHOR]

Rapid and quantitative determination of blood propofol concentration is important for anesthesiologists to accurately control intraoperative propofol dose, timely monitor physiological statuses of patients and greatly improve the safety of surgery. Herein, a dopant-assisted negative photoionization ion mobility spectrometer with the optimized ionization region structure and the three-way inlet design was developed, increasing the generation ratio of the reactant ions O 2 −, and improving the ionization efficiency of propofol molecules. Besides, the addition of methanol-anisole solution during injection promoted the neutral desorption of propofol in blood, further improving the detection sensitivity by an order of magnitude, eliminating any sample pretreatment and effectively reducing the single analysis time to less than 1 min compared to the previous article. The dual calibration quantitative method, i.e. the method of calibrating the O 2 − concentration and the sample concentration changes during the entire process of detecting propofol through the integral value of M·O 2 − and the maximum signal intensity of O 2 −, successfully achieved accurate quantification of blood propofol. And the linear calibration curve of propofol was obtained with the range of 0.1–15 ng μL−1 and with the limit of detection of 0.03 ng μL−1, which was fulfilled to conduct propofol determination throughout the perioperative period. Finally, this method was applied to clinically measure the blood propofol concentration in patients newly regained consciousness with concentrations ranging from 0.2 ng μL−1 to 3 ng μL−1, and it turned out that the older patient had the lower propofol concentration in blood. Image 1 • An ion mobility spectrometer for rapid and direct detection of blood propofol throughout perioperative period. • The methanol-anisole solution for enhancing neutral desorption and shortening the analysis time of propofol in blood. • Dual calibration quantification of propofol with the limit of detection reaching 0.03 ng μL−1 in less than 1 min. • Successful analysis of blood propofol in patients newly regaining consciousness after surgery. [ABSTRACT FROM AUTHOR]

Trimethylamine (TMA) is ubiquitous in the marine systems and may affect atmospheric chemistry as a precursor and strong stabilizer of atmospheric secondary aerosol, influencing cloud formation. Rapid and accurate measurement of the concentration of TMA in seawater is challenging due to their polarity, aqueous solubility, volatility and existence at low concentrations in marine environments. In this study, a dopant-assisted atmospheric pressure photoionization time-of-flight mass spectrometry (DA-APPI-TOFMS) coupled with a dynamic purge-release method was developed for rapid and sensitive analysis of TMA in seawater. A novel three-zones ionization source has been developed for improving the ionization efficiency of analyte molecules and minimizing the influence of high-humidity of the sample gas, which allowed direct analysis of high-humidity (RH> 90%) gas samples from microbubble purging process by the mass spectrometer. At atmospheric pressure, the three-zones ionization source allows the use of high-speed purge gas to quickly purge all organic amines dissolved in the water into the gas phase, ensuring quantitative accuracy. The limit of quantification (LOQ) for TMA down to 0.1 μg L−1 was obtained in less than 2 min by consuming only 2 mL seawater sample. This method was applied for the determination of the concentrations of TMA in the coastal seawater to validate its practicability and reliability for analysis of trace amines in marine environments. Image 1 • Dynamic purge-release combined with dopant-assisted APPI-TOFMS. • A novel three-zones ionization source has been developed for improving the ionization efficiency and minimizing the influence of high-humidity. • The limit of quantification for TMA down to 0.1 μg L-1 was obtained in less than 2 min by consuming only 2 mL seawater sample. [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]

The concentration of propofol in blood is an important indicator for anesthesiologists to monitor and regulate the anesthesia depth of patients during surgery. Herein, a negative photoionization ion mobility spectrometry with acetone as the dopant was developed for rapid and direct determination of intraoperative blood propofol concentration in the operating theatre. High concentration of acetone molecules in the carrier gas was used not only to enhance neutral desorption and release free propofol molecules from the whole blood, but also to increase the intensity of reactant O 2 − and reduce the amount of non-reactive CO 3 − ions simultaneously, which allowed to measure trace propofol in less than 2 min without any tedious pretreatment. Under optimized conditions, a linear calibration curve of propofol was obtained with the range of 0.5–20 ng μL−1 and with a limit of detection of 0.14 ng μL−1, which met the clinical requirements and correlated well with standard HPLC methods. Finally, the method was applied to detect intraoperative blood propofol concentration in nearly 100 surgical patients, demonstrating its excellent detection capability and facilitating the study of propofol pharmacokinetics. Image 1 • A negative photoionization ion mobility spectrometry for rapid and direct detection of propofol in whole blood. • High concentration of acetone as the dopant for enhancing neutral release and ionization reaction of propofol. • Accurate quantitative detection of propofol with LOQ reaching 0.5 ng μL−1 in less than 2 min. • Successful analysis of intraoperative blood propofol in real clinical situations. [ABSTRACT FROM AUTHOR]

Online monitoring of end-tidal propofol provides important information of anesthesia deepness for anesthetists as propofol concentrations in plasma and breath are well correlated. In this work, a dopant-assisted photoionization positive ion mobility spectrometry (DAPI-PIMS) coupled with time-resolved purge introduction was developed for online quantitative monitoring end-tidal propofol. With optimized dopant, toluene, the selectivity and sensitivity of propofol was improved as interference from sevoflurane was eliminated. Using the time-resolved purge introduction, the response of propofol and moisture was separated due to their absorption differences on the inwall of the fluorinated ethylene propylene (FEP) sample loop, ensuring sensitive measurement of end-tidal propofol with a short response time of 4 s. The quantitative equation derived from the second order reaction kinetics model extended the quantitative range of propofol from 0.2 ppbv to 45 ppbv. Finally, the method was used to monitor the intraoperative end-tidal propofol of six patients, and the results nicely demonstrated its feasibility in practical clinical environment. [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]