Application Research Of Dispersive Liquid-liquid Microextraction In The Determination Of Pyrethroid Residues

Sample preparation is an important step in the analysis of actual samples, especially for the determination of trace levels of analytes in complex matrices. Traditional pretreatment methods are gradually changing to be miniature and economic so as to lower cost and pollution. Dispersive liquid-liquid microextraction (DLLME) is precisely a new simple, economical and environment-friendly preparation technique. This work investigated the extraction efficiency of DLLME and improved its applications in complex samples, with the pyrethroids as the representative analytes.Firstly, this work summarized the research of the extraction-separation techniques in sample pretreatment, and outlined the development and applications of DLLME. Then, DLLME combined with gas chromatography (GC) was developed for the simultaneous determination of nine pyrethroids in river water by means of ultrasound-assisted emulsification, which markedly improved the extraction efficiency and shortened the time. Based on that, the real samples were further extended to more complex biological samples (pear). The factors which had significant impact on the extraction efficiency were investigated and optimized. Methodological study showed that the method was simple, rapid and environmentally friendly with less organic solvent.Finally, the combination of solid-phase extraction (SPE) and DLLME, coupled with gas chromatography-electron capture detection (GC-ECD) was developed to overcome the drawback of DLLME and establish a new pretreatment method that can selectively enrich, purify and detect trace drug residues in more complex samples. The SPE sorbents, washing solvent and eluent type, loading volume, eluent amount, extractant and dispersant dosages were optimized. Methodology validation and practical detection indicated that the enrichment factor, purification effect and detection limits of the method were all satisfactory.