Research On FAIMS Technology For Detection Of Volatile Organic Compounds

With the rapid development of industry and the dramatic increasement of civilian car,the volatile organic compounds（VOCs）in the environment have being increased year by year,thus caused seriously environmental problems.The assessment and governance of environmental pollution depends on rapid and on-site analytical detection techniques.The high-Field Asymmetric Waveform Ion Mobility Spectroscopy（FAIMS）as a powerful tool used for detection,filtration and characterization of ions in gas-phase has been applied in amount fields,which separation ions based on the normalized field dependences of ion mobility under high electric field.It has many unique advantages,including short detection time,high sensitivity,miniaturized and working at atmospheric pressure.Therefore,the utilization of FAIMS is expected to provide a technical support for detection of VOCs.In this works,a FAIMS experimental system with small volume,high sensitivity and great stability was constructed.It was composed of stable gas control system,continuous injection system and intelligent measurement and control system.It integrated a direct and clean ion source,a minimalized analyzer with shape of 75×24×4.5 mm³,a high-frequency and high-amplitude power supply with a frequency of 1MHz and amplitude of0-2 KV,and an ultra-weak current detector with a gain range of 10⁴¹0¹³.Based on this system,the influence of mixed carrier gas on FAIMS resolution was investigated secondly.The results showed that the proportion of He in mixed carrier gas made a big difference on resolution,and the resolution of various VOCs,including o-xylene,acetic acid,acetone,isobutane and n-hexane,was improved obviously under different proportions.Finally,the detection of benzene in water and the identification of differently labeled gasolines（92#,95#,98#.）were investigated separately.The experimental results showed that the detection limit of benzene in water was 0.89 ug/L,which was much lower than the national standard limitation 10 ug/L in drinking water.In addition,the accurate identification of different labeled gasolines was achieved by solving the second-order coefficientsα₂ and fourth-order coefficientsα₄ of the alpha dependence,which is a unique ion property determined by the interaction of the ion species with neutrals.