Application Of Liquid-phase Microextraction Based On Solidification Of Floating Organic Droplet Coupled With Gas Chromatography In The Analysis Of Pesticide Residues

Conventional sample preparation methods such as liquid-liquid extraction and solid phase extraction, are time-and solvent-consuming, and often involve several complicated procedures. A novel liquid phase microextraction (LPME) based on solidification of floating organic droplet (LPME-SFO) has been recently developed which was based on the distribution of the analytes between microliters volume of the extraction solvent (floating on the surface of the aqueous sample) and the aqueous sample matrix. The advantages of LPME-SFO method are simplicity of operation, rapidity, low-cost, high recovery and high enrichment factor.The recent developments of-the determination methods for pesticide residues and sample pre-treatment technologies were breifly summarized in the first part. A detailed review concerning the development of SFO-LPME and its applications were presented.In the second part, a novel method for the determination of triazine herbicides residues in water samples by LPME-SFO coupled with capillary gas chromatography with flame photometric detector (GC-FPD) was developed. Some significant parameters that affect the extraction efficiency, such as the extraction time, the kind and volume of the extraction and disperser solvent, were investigated. Under the optimum conditions, as high as 457 to 1501-fold enrichment factors were achieved. A good linear relationship was obtained in the range of 0.04-1000μg/L of the analytes, with the limits of detection of 0.005-0.8μg/L and the correlation coefficients of 0.9982-0.9990. This method has been applied in real water samples for the determination of pyrethroid pesticide residues (tap water, well water and river water) with satisfactory results. The recoveries ranged from 79.6%-106.0% and the relative standard deviations fall between 3.4% and 7.4%。In the third part, a method for the determination of eight pyrethroids in water samples by LPME-SFO coupled with GC-ECD was developed. Some experimental parameters that influence the extraction efficiency were studied and optimized to obtain the best extraction results. The limits of quantification (LOQs) ranged between 2.0 and 50 ng/L. The linear signal was observed in the range from (their corresponding LOQs) 0.15 to 80.0μg/L for all the pyrethroids with the correlation coefficients (r) ranging from 0.9961 to 0.9988. The RSDs for five replicate experiments varied from 4.1% to 8.7%.In the fourth part, a method was developed for the determination of amide herbicides in water samples by LPME-SFO coupled with GC-ECD. Some experimental parameters that influence the extraction efficiency were studied and optimized. The LOQs ranged between 0.03 and 1.0μg/L. The linear signal was observed in the range from (their corresponding LOQs) 0.01 to 200μg/L for all the herbicides with the correlation coefficients (r) ranging from 0.9965 to 0.9994. The RSDs for five replicate experiments varied from3.6% to 7.3%.