Study on Highly Sensitive and Rapid Detection Technology for Isoprene and -Pinene by Ultraviolet Photoionization High-Field Asymmetric Waveform Ion Mobility Spectrometry

Biogenic volatile organic compounds (BVOCs) account for about 90% of the total VOCs emissions in the atmosphere and have an essential impact on the atmospheric environment. In this work, a method based on a self-made ultraviolet photoionization high-field asymmetric waveform ion mobility spectrometer (UV-FAIMS) was used for sensitive and rapid detection of isoprene with the most significant proportion in BVOCs and alpha-pinene with the largest proportion in monoterpenes. The characteristic identification parameters, linear range, detection limit and mixture identification ability were studied. By collecting the UV-FAIMS ion spectra of isoprene and alpha-pinene with separation voltage from 0 to 1260 V, the nonlinear function coefficients alpha(2) and alpha(4) for feature recognition were obtained, which provided a reference for the optimization of the detection parameters of UV-FAIMS. The FAIMS spectra of isoprene with concentration of 28-896 mu g/m(3) and alpha-pinene with concentration of 45-1440 mu g/m(3) were acquired and analyzed, showing that the linearity of their responses (Correlation coefficient, R) reached 0.998 and 0.997, respectively. The detection limit (S/N=3) reached 15 and 10 mu g/m(3), respectively. The FAIMS spectra of the isoprene sample with a concentration of 1400 mu g/m(3), the alpha-pinene sample with a concentration of 560 mu g/m(3), and the mixture of the two samples were acquired and analyzed, showing that UV-FAIMS had the ability to identify mixture of isoprene and alpha-pinene. The peak position deviations of a single sample's characteristic ion peaks and the mixture's multi-peak fitting results were only 2.2% and 4.9%.