Research On Monitoring Technology And Data Processing Method Of VOCs Based On Gas Chromatography

Volatile organic compounds(VOCs)is of great significance in atmospheric chemistry.It’s vital precursors of ozone,photochemical smog,secondary organic aerosol and PM2.5.VOCs has a very important impact on atmospheric oxidation capacity,the formation of second organic pollutants and human health.Because of the complexity and harmfulness of VOCs components,and chemical changes easily occurring in air,it has become a hot topic of environmental chemistry research in recent years.In this paper,a data processing software is designed and realized for ambient air VOCs monitoring system.The software consists of three parts:human-computer interaction,sample calibration and data processing.It can realize the control and data reading of the thermal desorption device and the gas chromatography.At the same time,according to the characteristics of VOCs spectrum,we choose the appropriate data processing method to ensure the veracity of qualitative and quantitative calculation.Aiming at the situation that the VOCs spectrum contains high frequency noise and baseline drift,wavelet transform is applied to deal with it.By selecting suitable wavelet function and optimal decomposition layer number,the removal of high frequency noise and correction of low frequency baseline drift can be completed at the same time.The two processes merge into one can improve the speed of data processing.The first and two order derivative combining method is studied to identify the chromatographic peaks.This method is simple in calculation and fast in running speed,and can have good recognition accuracy for irregular peaks such as overlapping peaks and shoulder peaks.In view of the overlapping of chromatographic peaks,based on the principle of least squares,the Gauss function is used to fit the curve fitting to separate the overlapped peaks.Compared with the traditional vertical line method,it has a higher calculation precision of peak area.At the same time,the spectral peak analysis method studied in this paper is compared with the spectral peak analysis method in Origin software,and the results are in good agreement.Therefore,the data processing software designed in this paper has high reliability.The designed data processing software is applied to the ambient air VOCs monitoring system,and the air VOCs sampling experiment is carried out.During the experiment,the software runs stably and the result is accurate.To sum up,the data processing software designed and implemented in this paper can meet the requirements of environmental atmospheric VOCs chromatogramprocessing,and can provide practical and reliable data for environmental assessment.