| Samples pretreatment is time-consuming and easy to bring measurement error. The traditional sample pretreatment methods such as liquid-liquid extraction, solid phase extraction suffer from the disadvantage of tedium and a great deal of toxic organic solvent to be used and so on. In recent years, a lot of research workers have focused on the development of new sample preparation methods, which are less time-consuming, economical, efficient and environmentally friendly. Dispersive liquid-liquid microextraction (DLLME), introduced by Rezaee et al in2006, is a novel liquid-liquid microextraction technique, which is a simple and fast microextraction technique based on homogeneous liquid-liquid microextraction (HLLE) and cloud point extraction (CPE). The method usually need only10microliter of extractant. In the process of extraction, the well dispersion of the extraction solvent (assisted by the disperser solvent) in the aqueous solution will lead to the generation of a significantly large contact area between the extraction solvent and the aqueous phase. The equilibrium is quickly reached and the analyte is enriched in a short time. It also has other advantages such as simplicity of operation, low cost, high enrichment factor and recovery and environment friendly.This work combines dispersive liquid-liquid microextraction with gas chromatography-flame ionization detection (GC-FID), has established a new sample pretreatment method to analyse plasticizer and pesticide residues in environment samples. The main research contents are as follows:(1)A simple and efficient method for the simultaneous extraction and determination of four plasticizer (diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, dioctyl phthalate) residues in wine samples was developed using dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-flame ionization detection (GC-FID). The parameters, including type and volume of extractant and dispersant, extraction time and salt amount on the extraction performance were investigated and optimized in detail. Under the optimal conditions:30μL CCl4was used as extraction solvent,0.75mL isopropanol was used as disperser solvent,1%(w/v) NaCl and60s extraction time, good linearity was observed for all analytes in the range of1-200μg L-1with correlation coefficients (r2)>0.9938. The limits of detection (LODs) for the analytes based on signal-to-noise of3were between0.34and0.75μg L-1. The enrichment factors for the four plasticizer residues were ranged from233,473,340and340folds. The precision for these analytes, as indicated by relative standard deviations (RSDs) were less than6.12%(n=5), for both intra-and inter-day analysis. The proposed method was successfully applied for the preconcentration and determination of four plasticizer residues in the two wine samples with mean recoveries in the range of86.5%-106.4%.(2)A simple and efficient method for the simultaneous extraction and determination of six pesticide residues (prometryn, buprofezin, trizophos, λ-cyhalothrin, pyridaben, esfenvalerate) in water samples was developed using ultrasonic-assisted dispersive liquid-liquid microextraction (UA-DLLME) combined with gas chromatography-flame ionization detection (GC-FID). The parameters, including type and volume of extractant and dispersant, extraction time and salt amount on the extraction performance were investigated and optimized in detail. Under the optimal conditions:15μL CCl4was used as extraction solvent,1.00mL acetonitrile was used as disperser solvent,5min extraction time and no salt added, good linearity was observed for all analytes in the range of1～100μg L-1with correlation coefficients (r2)≥0.9990. The limits of detection (LODs) for the analytes based on signal-to-noise of3were between0.09and0.57μg L’1. The precision for these analytes, as indicated by relative standard deviations (RSDs) were less than4.82%(n=5), for both intra-and inter-day analysis. Further, the enrichment factors for the six pesticides were ranged from315to1153fold. The proposed method was successfully applied for the preconcentration and determination of six pesticides in the environmental water samples (river water, tap water, lake water) with mean recoveries in the range of90.5%～107.7%. The proposed method could satisfy the requirements for the determination of different pesticide residues in water samples.(3)A simple and efficient method for the simultaneous extraction and determination of five pesticide residues (buprofezin, trizophos, λ-cyhalothrin, pyridaben, esfenvalerate) in water samples was developed using ultrasound-assisted dispersive liquid-liquid microextraction method based on solidification of floating organic droplet (UA-DLLME-SFO) combined with gas chromatography-flame ionization detection (GC-FID). Under optimal conditions:8μL1-dodecanol was used as extraction solvent (its toxicity was much lower than that of extraction solvent in traditional DLLME),300μL acetonitrile was used as disperser solvent,1%(w/v) NaCl,3min extraction time and5min centrifugation time at4000rpm, good linearity was observed for all analytes in the range of0.20μg L’1-200μg L-1(n=3) with correlation coefficients≥0.9976, enrichment factors were obtained between143and813. Limits of detection (S/N=3) ranged between0.11and0.48μg L-1, depending on the compounds. Relative standard deviations (%) were less than3.49%(n=5) for both intra-and inter-day analysis. The proposed UA-DLLME-SFO method was successfully applied for the determination of pesticides in water samples (river water, tap water, lake water) with mean recoveries that varied from94.10%to109.40%(RSDs<5.01%). |
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