Development of Ion Funnel Focusing Photoionization Mass Spectrometry and Its Application in Online Monitoring of Atmospheric Benzene Series

Atmospheric benzene series have high photochemical reactivity and biological toxicity,and have been one of the most important atmospheric volatile organic pollutants. However,their low concentration and rapid temporal and spatial changes make real-time and accurate quantitative monitoring extremely challenging. Vacuum ultraviolet photoionization (VUV-PI)mass spectrometry is a commonly used analytical method for online monitoring of benzene series,but the currently commonly used VUV-PI ionization source cannot effectively utilize the generated ions,which restricts the further improvement of sensitivity. In this study,a novel ion funnel focused photoionization time-of-flight mass spectrometer (IFPI-TOFMS)was developed. By introducing a radio frequency ion funnel into the photoionization source,the ion transmission efficiency in the source was increased by 26-37 times,and the limits of detection (LODs)of IFPI-TOFMS for isoprene, benzene,toluene, styrene, p-xylene,trimethylbenzene, and limonene reached 34. 3 x 10(-12),7. 9 x 10(-12), 7. 0 x 10(-12),9. 4 x 10(-12),7. 7 x 10(-12),10. 6 x 10(-12) and 13. 7 x 10(-12)(V/ V)within 5 s,respectively. Linear range of 2-3 orders of magnitude were achieved with the linear correlation coefficients (R-2)greater than 0. 99. The relative standard deviation (RSD)during 12 h monitoring was less than 3%,which exhibited good stability of IFPI-TOFMS. IFPI-TOFMS was utilized to carry out real-time online monitoring of atmospheric benzene series in Dalian urban area. The results showed that benzene series in the atmosphere down to 10(-12) (V/ V) could be quantitatively monitored in real-time and online by IFPI-TOFMS,which indicated that IFPI-TOFMS had potential application value and broad development prospects in the field of atmospheric environment monitoring.