Application Study Of Dispersive Liquid-liquid Microextraction For The Analysis Of Pesticide Residues In Fruit Juices Samples

With the improvement of people’s living standards and the popularization of health knowledge, more and more consumers are preferring healthy fruit juice. However, the safety problem caused by pesticide residues is increasingly becoming one focus of attention.To control effectively the pollution of pesticide residues and ensure the quality and safety of fruit juice, the fast, reliable, high sensitive and low cost analytical techniques are imperative. Analytical methods developed to determine pesticide residues include gas chromatography (GC) and liquid chromatograph (LC). Gas chromatography is used widely due to the advantages of efficient separation, high sensitivity and high popularity, especially in the field of food and agricultural products. Compared with liquid chromatograph coupled with ultraviolet detector (UVD) or diode array detector (DAD), gas chromatograph equipped with electron captured detector (ECD) or flame photometric detector (FPD) has the advantages of high sensitivity and high selectivity for many pesticides.The quick and effective sample preparation techniques coupled with the reliable analytical methods are necessary. Sample preparation has been playing an important role in the research field of pesticide residues analysis. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) are the common sample preparation methods widely used for residue analysis. Recently, a growing number of studies have focused on two kinds of microextractions termed as liquid-phase microextraction (LPME) and solid-phase microextraction (SPME). Later in2006, Rezaee et al. developed a novel liquid-liquid microextraction method named as dispersive liquid-liquid microextraction (DLLME). It possesses obvious advantages of simple operation with rapidity, low cost, high enrichment factor, low consumption of organic solvent, and environmental benignity.In this paper, the pesticide residues types and harm of fruit juice, the detection methods of pesticide residues, and the new techniques of sample preparation were summarized. Status on the research of sample pretreatment techniques were specifically reviewed. Importantly, the principle, procedures, and the application for the pesticide residues analysis of dispersive liquid-liquid microextraction were introduced. On the basis of current trends of dispersion liquid microextraction, some new preparation techniques was developed, the result was satisfactory. The details and results are as follows:A novel method was developed for the analysis of organophosphorus pesticides residues in fruit juice using dispersive liquid-liquid microextraction coupled to gas chromatography with flame photometric detector (GC-FPD). Parameters affecting the extraction performance, such as the properties and volume of extraction and dispersive solvents, extraction time and salt concentration, were studied and optimized. Under the optimum extraction conditions, the enrichment factors ranged from106to147for eight organophosphorus pesticides, and the limits of detections of the method were in the range of0.03～0.2μg/L (S/N=3). The developed method was successfully applied for the determination of pesticides multiresidue in variety of fruit juices, and the average spiked recoveries ranged from74.7to128.0%, and relative standard deviations(RSDs) is less than6%. Results showed that the method could completely meet the requirement for the determination of pesticide residues in fruit juices.Dispersive liquid-liquid microextraction combined with gas chromatography-electron capture detection (GC-ECD) was used for the quantitative analysis of ten pyrethroids (tetramethrin, bifenthrin, lambda-cyhalothrin, permethrin, cyfluthrin, cypermethrin, flucythrinate, fenvalerate, tau-fluvalinate and deltamethrin) in different fruit juices including apple, pear, grape and peach juices. In a systematic investigation, various factors such as the types and volumes of extraction solvents and dispersive solvents played an important role in DLLME. Under the optimum conditions, high enrichment factors were obtained ranging from64to110. Ten pyrethroids were separated within29min using a DB-1capillary column. The satisfactory linearity was observed in the range of0.0002-10mg/L with good correlation coefficient (r2)≥0.9990. The limits of detections were from0.2to2μg/L (S/N=3). The recoveries of this method evaluated at two spiked levels of0.01and0.1mg/L ranged from61.3%to108.4%with relative standard deviations below7%. In addition, the proposed method was successfully applied to determine pyrethroids residues in real fruit juices, whose identities were assigned by comparison of retention times with standard substances and further confirmed by gas chromatography-mass spectrometry (GC-MS).A novel technique composed of the quick, easy, cheap, effective, rugged and safe (QuEChERS) and dispersive liquid-liquid microextraction sample preparation coupled with gas chromatography-electron capture detection was developed for the determination of ten pyrethroid residues in different fruit juices (orange, lemon, kiwi and mango). The sample preparation involved the quick extraction of fruit juices with acetonitrile in presence of anhydrous MgSO4and NaCl. Then, the extract was purified by primary secondary amine (PSA) sorbent, followed by DLLME using carbon tetrachloride as extractive solvent and the extract obtained by QuEChERS as dispersive solvent. Under the optimum conditions, the enrichment factors were achieved ranging from16to26. Ten pyrethroids were separated within29min using a DB-1capillary column. The satisfactory linearity was observed in the range of0.0002～10mg/L with good correlation coefficient (r2)≥0.9990. The recoveries of the method evaluated at two spiked levels of0.01and O.lmg/kg ranged from62.6to137.5%with relative standard deviations below9%. The limits of quantification were between0.2and1.4μg/kg (S/N=10) lower than O.Olmg/kg. In addition, the applicability of the method was successfully demonstrated with fruit pulps contaminated by pyrethroid residues, whose identities were assigned by comparison of retention times with standard substances and further confirmed by gas chromatography-mass spectrometry.