Applications On Dispersive Liquid-liquid Microextraction For Determination Of Volatile Organic Compounds And Organochlorine Pesticides

The development trend of modern analytical chemistry is miniaturization,simplification and automation.Dispersive liquid-liquid microextraction(DLLME)is a simple,fast,and miniaturized sample preparation technique,which incorporates sampling,extraction and enrichment into one step.A number of works have been reported about the determination of a vast variety of organic and inorganic compounds in different matrices since its introduction in 2006.The purpose of this study was to develop novel alternatives of dispersive liquid-liquid microextraction coupled with GC-MS to analysis of chemical compounds in essential oils and aromatic water of plants,and organochlorine pesticides(OCPs)in water samples.A brief description was given as follows:(1)A simply overview about the principles,factors affecting the extraction efficiency and detail review of the improvement in dispersive liquid-liquid microextraction.The main focus is on the application of organic compounds by DLLME and improvements of the type of extraction solvent,the mode of dispersion,the way of demulsification and so on.(2)A novel method was successfully developed for extraction and preconcentration of essential oil from flowers of Edgeworthia chrysantha Lindl.by using ultrasound-assisted extraction/dispersive liquid-liquid microextraction(UAE-DLLME)coupled with gas chromatography-ion trap/mass spectrometry(GC-IT/MS)using a direct sample introduction(DSI)device.The optimum parameters of UAE-DLLME were investigated.Under the optimum extraction conditions,36 substances were identified.The results demonstrated that UAE-DLLME coupled with DSI-GC-MS is a simple,rapid,non-expensive and environmentally friendly method and the proposed method could extract more semi-volatile compounds in essential oils of plants.The essential oil compounds of Edgeworthia chrysantha Lindl.identified by this method were more comprehensive.(3)A novel low-density solvent-based ultrasound-assisted surfactant-enhanced-emulsification liquid-liquid microextraction(LDS-USLLME)was developed for determination of 15 organochlorine pesticides(OCPs)in water samples followed by gas chromatography-mass spectrometry(GC-MS).The influences of various experimental parameters were investigated.Under the optimized conditions,the method provided a good linearity of calibration curve with good correlation coefficients(R2>0.99),low limits of detection,and RSD values lower than 12.3%(n=5).To examine the influence of matrix effects,secondary addition recovery experiments were carried out to analyze OCPs in tap water.Results implied that there was no significant interference for the determination of OCPs in water samples.The proposed LDS-USLLME-GC/MS method was demonstrated to be simple,practical,and environmentally friendly for the determination of trace organochlorine pesticides in water samples.(4)The essential oil of Mentha haplocalyx Briq.was extracted by steam distillation(SD),microwave-assisted extraction(MAE)and ultrasonic microwave-assisted extraction(UMAE)and aromatic water was collected at the same time.Volatile compounds in aromatic water were extracted by ultrasound-assisted surfactant-enhanced emulsification liquid-liquid microextraction(USLLME).The components in essential oil and aromatic water of Mentha haplocalyx Briq.were separated and identified by GC-MS.The results showed that the extraction rates of volatile oil were 1.12%,0.87%and 0.98%,respectively.The main identified compounds were menthol,menthone,isomenthone,pulegone,and piperitone.Most of the effective compounds existed in aromatic water of Mentha haplocalyx Briq.were the same as the one in its essential oil.The results indicated that MAE and UMAE are alternatives to SD in comparison with extraction time.More essential oil compounds were extracted by UMAE which is an efficient,rapid,simple and green preparation technique for extraction of essential oils from plants.The proposed method of USLLME was also a simple,fast,efficient and convenient method for the extraction of volatile compounds in aromatic water of Mentha haplocalyx Brig..