Dopant titrating ion mobility spectrometry for trace exhaled nitric oxide detection

Selective measurement of Cl2 and HCl based on dopant-assisted negative photoionization ion mobility spectrometry combined with semiconductor cooling

This study presents an efficient approach for the precise detection of chlorine gas (Cl2) and hydrogen chloride (HCl), harmful pollutants frequently emitted from chlor-alkali and various industrial processes. These substances, even in trace amounts, pose significant health risks. Ion mobility spectrometry (IMS), known for its sensitivity in pollutant detection, traditionally struggles to differentiate between Cl2 and HCl due to the similarity of their product ions, Cl-. To overcome this limitation, we introduce a novel technique combining dopant-assisted negative photoionization ion mobility spectrometry (DANP-IMS) with an automatic semiconductor cooling system. This unique combination utilizes the differential cryogenic removal efficiencies of Cl2 and HCl to segregate these gases before analysis. By applying DANP-IMS, we achieved selective measurement of Cl- ion signal intensities under both standard and cryogenic conditions, facilitating the accurate quantification of total chlorine and Cl2 levels. We then determined HCl concentrations by deducting the Cl2 signal from the total chlorine readings. Our approach demonstrated detection limits of 2.0 parts per billion (ppb) for Cl2 and 0.8 ppb for HCl, across a linear detection range of 0-200 ppb. Moreover, our method's capability for real-time atmospheric monitoring of Cl2 and HCl near industrial sites underscores its utility for environmental monitoring, offering a robust solution for the separate and precise measurement of these pollutants.

Benzene-assisted photoionization positive ion mobility spectrometry coupled with a time-resolved introduction for field detecting dimethyl sulfide in seawater

Biogenic dimethyl sulfide (DMS) has attracted widespread attention over several decades due to its potential role in linking ocean biology and climate. The air-to-sea exchange flux, estimated based on marine DMS concentration, offers useful information for evaluating its contribution to climate change. As such, field observation techniques with the characteristics of fast testing speed, portability and easy operation are in demand to accurately monitor the DMS in seawater. In this paper, we proposed a new strategy for the sensitive field measurement of DMS in seawater based on benzene-assisted photoionization positive ion mobility spectrometry (BAPI-PIMS) coupled with a time-resolved introduction. Benzene was employed as a dopant to improve the selectivity by keeping the other sulfur compounds from being ionized, while the two-dimensional data versus drift time and retention time were obtained via an online separating column to eliminate the adverse impact of environmental moisture. Under the optimization conditions, the LODs (S/N = 3) for two product-ion peaks (PIPs) of DMS decreased to 0.081 nmol L^-1. Finally, the established method was applied to the lab and ship-board analysis of seawater from the Bohai Sea and the North Yellow Sea in the summer of 2019, and DMS in surface seawater was in the range of 0.11-23.90 nmol L^-1 with an average of 9.88 ± 6.96 nmol L^-1, indicating the potential for the field detection of marine DMS.

Long-term sub second-response monitoring of gaseous ammonia in ambient air by positive inhaling ion mobility spectrometry

A real-time dynamic measurements of ammonia (NH₃) is crucial for understanding the atmospheric nucleation process. A novel method was developed for on line monitoring at the sub-second time scale for the gaseous ammonia in ambient air for months, based on a positive inhaling ion mobility spectrometry (IMS) with a ⁶³Ni ion source. The selective detection of NH₃ was achieved using a high resolution IMS with an optimization of the drift tube temperature above 150°C. This method improved the peak-to-peak resolution significantly, thus avoided the interferences of the adjacent peaks to the quantitative analysis of NH₃. The time resolution of the IMS was less than 0.1s at a data averaging of 10 times. The limit of detection (LOD) achieved at sub-ppb level while a linear response of peak intensity versus concentration of NH₃ in the range of 10-60ppb and 60-400ppb were obtained. The relative standard deviations (RSD), the confidence level and the errors were 1.06%, 95% and ± 0.21ppb by measuring 100ppb NH₃ for 100 times. The effect of ambient humidity could be greatly reduced by using the drift temperature of over 150°C. At last, the application of measuring the NH₃ concentration evolutions of Dalian city was performed from June 19 to December 3 in 2015. The results illustrated a potential method of using IMS for a real-time measuring atmospheric NH₃ at an unprecedented accuracy and sensitivity with long-term stability.

A Novel Microwave-Induced Plasma Ionization Source for Ion Mobility Spectrometry

This work demonstrates the application of a novel microwave induced plasma ionization (MIPI) source to ion mobility spectrometry (IMS). The MIPI source, called Surfatron, is composed of a copper cavity and a hollow quartz discharge tube. The ion mobility spectrum of synthetics air has a main peak with reduced mobility of 2.14 cm2V-1s-1 for positive ion mode and 2.29 cm2V-1s-1 for negative ion mode. The relative standard deviations (RSD) are 0.7% and 1.2% for positive and negative ion mode, respectively. The total ion current measured was more than 3.5 nA, which is much higher than that of the conventional 63Ni source. This indicates that a better signal-to-noise ratio (SNR) can be acquired from the MIPI source. The SNR was 110 in the analysis of 500 pptv methyl tert-butyl ether (MTBE), resulting in the limit of detection (SNR = 3) of 14 pptv. The linear range covers close to 2.5 orders of magnitude in the detection of triethylamine with a concentration range from 500 pptv to 80 ppbv. Finally, this new MIPI-IMS was used to detect some volatile organic compounds, which demonstrated that the MIPI-IMS has great potential in monitoring pollutants in air.

Fractional exhaled nitric oxide-measuring devices: technology update

The measurement of exhaled nitric oxide (NO) has been employed in the diagnosis of specific types of airway inflammation, guiding treatment monitoring by predicting and assessing response to anti-inflammatory therapy and monitoring for compliance and detecting relapse. Various techniques are currently used to analyze exhaled NO concentrations under a range of conditions for both health and disease. These include chemiluminescence and electrochemical sensor devices. The cost effectiveness and ability to achieve adequate flexibility in sensitivity and selectivity of NO measurement for these methods are evaluated alongside the potential for use of laser-based technology. This review explores the technologies involved in the measurement of exhaled NO.

Online Measurement of Exhaled NO Concentration and Its Production Sites by Fast Non-equilibrium Dilution Ion Mobility Spectrometry

Exhaled nitric oxide (NO) is one of the most promising breath markers for respiratory diseases. Its profile for exhalation and the respiratory NO production sites can provide useful information for medical disease diagnosis and therapeutic procedures. However, the high-level moisture in exhaled gas always leads to the poor selectivity and sensitivity for ion spectrometric techniques. Herein, a method based on fast non-equilibrium dilution ion mobility spectrometry (NED-IMS) was firstly proposed to directly monitor the exhaled NO profile on line. The moisture interference was eliminated by turbulently diluting the original moisture to 21% of the original with the drift gas and dilution gas. Weak enhancement was observed for humid NO response and its limit of detection at 100% relative humidity was down to 0.58 ppb. The NO concentrations at multiple exhalation flow rates were measured, while its respiratory production sites were determined by using two-compartment model (2CM) and Högman and Meriläinen algorithm (HMA). Last but not the least, the NO production sites were analyzed hourly to tentatively investigate the daily physiological process of NO. The results demonstrated the capacity of NED-IMS in the real-time analysis of exhaled NO and its production sites for clinical diagnosis and assessment.