A New Liquid Phase Microextraction And Its Application In Determining Residues Of Aromatic Amines,Carbaryl And Triazophos Pesticides

Aromatic amines are widely used as intermediates in the dye,photographic, pharmaceutical and pesticide industries and as antioxidants in the polymer industry. They may be released into the environment directly as a result of discharge from factories or indirectly as a degradation of phenylcarbamates,anilide herbicides and azo dyes.Due to their high solubility in water,aromatic amines can easily permeate through soil and contaminate ground water.Because they are suspected to be carcinogenic and highly toxic to aquatic organisms,several of them have been listed on the priority blacklist released by US Environmental Protection Agency since 1970s.Organophosphates and N-methylcarbamates,as alternatives to the high persistent and bioaccumulating organochlorine compounds,are two important classes of insecticides.Because of their broad spectrum of activity,they have been widely used on a variety of crops in the current Chinese agricultural practices.However,since they are inhibitor of acetyl-cholinesterase,many of these compounds display high acute toxicity and are suspected for mutagenic carcinogenic and endocrine disruptor effects.As these organic pollution and pesticides poses a great threat to enviroment and human health,it is necessary that a simple,economic and rapid method be developed to determine the residue,at trace level,of these compounds in environmental matrices.Liquid-phase microextraction(LPME) is developed as a solvent-minimized preconcentration technique,which is based on the distribution effect of the analytes between a microdrop of organic solvent and aqueous sample solution.This technique belongs to the green analytical technique and is suitable to the development of micromation of modern analytical science.It combines extraction,preconcentration and sample introduction in one step,and is proved to be a simple,fast and enviromental friendly sample preparation method.Up to now,several different models of LPME,such as static/single drop liquid-phase microextraction(S-LPME),dynamic liquid-phase microextraction(D-LPME),continuous-flow microextraction(CFME),headspace LPME,hollow fiber membrane LPME and dispersive liquid-liquid microextraction(DLLME) have been developed.Compared with the traditional LPME,the extraction time for the DLLME is very short and does not require special approach and instrument in the pre-treatment step.Since its introduction, this method has been applied for the determination of trace organic pollutants and metal ions in environmental liquid samples.In order to assess DLLME suitability for different kinds of compunds and matrix, aromatic amines(p-toluidine,o-chloroaniline,p-chloroaniline and p-bromoaniline), carbamate and organophosphate(carbaryl and triazophos) were selected as representative compounds;water,fruit juice and soil were selected as different matrix.High-sensitivity and fast methods to detect these compounds in environmental water,fruit juice and soil samples by the pretreatment of DLLME have been set up.The main conclusions obtained are listed as follows:Firstly,DLLME combined with HPLC-VWD has been applied to the analysis of four aromatic amines in East Lake and Yangtse River.Under the optimized conditions,the linearity was observed in the range of 5.0-5000 ng mL^-1 for the four compounds with coefficient of correlation(r²) ranged from 0.9990 to 0.9998.The enrichment factors varied between 41and 95.Limit of detection(LOD) were in the range of 0.8-1.8 ng mL^-1.The recoveries were 85.4-111.7%,and the RSD values were between 4.1 and 5.3%。Secondly,DLLME coupled with HPLC-FLD has been developed to determine carbamate(carbaryl) and organophosphorus(triazophos) pesticide residues in water(Ao river,East sea and tap water) and fruit juice(apple juice,grape juice and peach juice) samples.Linearity of calibration curve was observed in the concentration range of 0.1-1000 ng mL^-1 with correlation coefficients ranged from 0.9991 to 0.9999.The enrichment factors and the limit of detection for carbaryl and triazophos were 87.3 -275.6 and 12.3-16.0 pg mL^-1,respectively.The recoveries for the water and fruit juice were in the range of 80.4-114.2%and 86.3-117.8%,respectively.The RSD values were in the range of 1.38-2.74%,indicating good extraction repeatability.These results demonstrated that the water and fruit juice(1:1 dilution with water) matrices,used in this experiment,had little effect on DLLME efficiency.Finally,DLLME combined with HPLC-FLD has been developed to determine carbaryl and triazophos pesticides residues in soils.Methanol was first used as extraction solvent for the extraction of pesticides from the soils and then as dispersive solvent in the DLLME procedure.Under the optimum extraction conditions,the linearity was obtained in the concentration range of 0.1-1000 ng g^-1 for carbaryl and 1-5000 ng g^-1 for triazophos,respectively.Coefficients and the limits of detection(LODs) were in the range of 0.9997 -0.9999.and 14-110 pg g^-1,respectively.The recoveries were 80.8-111.1%and the RSD values were between 1.96 and 4.24%.These results demonstrated that the soil matrices,used in this experiment,had little effect on DLLME efficiency.