Application Of Ultrasonic/Microwave Assisted Extraction And Frozen Preconcentration In The Analysis Of Volatile Organic Compounds

microwave assisted extraction(MAE)as a fast and efficient extraction technology has been widely applied in extraction of natural products,food analysis and pharmaceutical analysis.Compared with static MAE mode,ultrasonic/microwave asstited extraction(UMAE)has more advantages,Ultrasonic accelerate the transfer rate of analytes from sample matrix into extraction solvent and the degradation of analytes could be avoided when increasing microwave irradiation time.In the published research on MAE,the extractant was usually water or traditional organic solvent.In this paper,sample was pretreated by deep eutectic solvent(DES),which made the species of extracting volatile organic compound(VOC)richer and the oil yield was higher.Environment VOC was detected by gas chromatography-mass spectrometry(GC-MS)primarily,however,when the VOC directly into the instrument there will be many problems.For example signal response is not high,poor mass spectral resolution,the instrument affected by the humidity and other issues.The above problems were improved by purifying and concentrating the sample by a three-stage cold trap technique.The details are as follows:1)A method for the extraction of star anise volatile essential oil by microwave assisted steam distillation(MASD)based on DES was established(DES-MASD).The parameters of the extraction process were optimized.Under the optimum conditions,the extraction of volatile essential oil was carried out,the essential oil yield of DES-MASD was 5.3%,the essential oil yield of MASD was 3.0%,and there was significant differences in the yield of essential oils.Analysis of essential oilcomponents,DES-MASD got more VOC than MASD.The experimental results show that DES-MASD is a new type of green pretreatment technology for efficient extraction of volatile essential oil from star anise.2)A novel DES-based ultrasonic/microwave assisted steam distillation(UMASD)headspace solid phase microextraction(SPME)coupled with GC-MS was developed to determine the volatile essential oil in star anise(DES-UMASD-SPME).The factors influencing the method were optimized by single factor experiment,and the optimal experimental conditions were obtained.The precision of the method was tested under optimal conditions was 7.3%.The results of the samples obtained under the optimal conditions were compared with DES-MASD,the DES-UMASD-SPME method used less sample and consumed lower DES volume and took shorter extraction time.The results show that DES-UMASD-SPME is a rapid and efficient experimental method for the rapid extraction and analysis of the volatile essential oil of star anise,consumption of less sample,no pollution,meeting the needs of green analytical chemistry.3)A method of enrichment and detection of VOC in the environment of three-stage cold trap pretreatment was established.The Capture temperature of the three-stage cold trap of the atmospheric preconcentration instrument was optimized,A series of tests were conducted on TO15 standard gas: The standard curve(0.5-10nmol/mol)was plotted to obtain the average relative response factor of the target compound,their relative standard deviation were between 4.47 and 28.12%;The accuracy of the method were 2.81-18.68%;The method detection limit(MDL)were0.22-2.17 nmol/mol;The recoveries of the obtained method were 72.51-113.67%.A sample of ambient air from a factory was tested and a high concentration of N,N-dimethylacetamide was present.The above experimental results show that the enrichment and detection method of VOC in the environment of three-stage cold trap pretreatment is an efficient and reliable method,it is low MDL,high sensitivity,no consumption of organic reagents,no pollution,conform with the need of environmental VOC monitoring,conform with the need of green analytical chemistry.