Photoionization-induced NO+ chemical ionization time-of-flight mass spectrometry for rapid measurement of aldehydes and benzenes in vehicles

Abstract

In-vehicle air pollution has become a major concern to public health in recent years. The traditional analytical methods for detection of volatile organic compounds (VOCs) pollutants in air are based on gas chromatography - mass spectrometry (GC-MS) or high-performance liquid chromatography (HPLC), including complicated pretreatment and separation procedures, which are not only time-consuming and labor-intensive, but also incapable of simultaneously measuring both aldehydes and benzenes. In this work, a new photoionization-induced NO⁺ chemical ionization time-of-flight mass spectrometry (PNCI-TOFMS) was developed for real-time and continuous measurement of aldehydes and benzenes in vehicles. High-intensity NO⁺ reactant ions could be generated by photoionization of NO reagent gas, and efficient chemical ionization between NO⁺ reactant ions and analyte molecules occurred to produce adduct ions M·NO⁺ at an elevated ion source pressure of 800 Pa. Consequently, the achieved LODs for aldehydes and benzenes were down to sub-ppbv within 60 s. The analytical capacity of this system was demonstrated by continuous and online monitoring of in-vehicle VOCs in a used car, exhibiting broad potential applications of the PNCI-TOFMS in air pollutants monitoring and in-vehicle air quality analysis.

Keywords: Aldehydes and benzenes; In-vehicle air; Photoionization-induced NO(+) chemical ionization; Rapid measurement; Time-of-flight mass spectrometry; Volatile organic compounds.