| Dispersive liquid-liquid microextraction is mainly used for the determination of thetarget analytes in aqueous matrix, and has been widely used in recent years. In thismethod, the extraction solvent is rapidly dispersed into the aqueous sample phase asfine droplets with the existence of dispersive solvent, which markedly increases thecontact surface between the extraction solvent and the aqueous sample and reducesthe extraction time.The first experiment of this paper applied DLLME-SFO as the method for thedetermination of four phenols in waters, including BPA, α-NAP, β-NAP and2,4-DCP. The optimal conditions were as follows:25μL of1-undcanol was served asthe extraction solvent; actone was used as the dispersive solvent, and its volume was125μL; the salt addition was adjusted to10%; and the most approprimate pH valuewas6.0. The linear range were0.01~2μg/mL, and the correlation coefficients(r)ranged between0.9993and0.9996; the enrichment factors (EF) varied from153.9to206.2; the limits of detection (LOD) were5.4~9.0ng/mL; the relative standarddeviations (RSD) were less than15.0%; the recoveries of the target analytes wereranged from64.2%~126.0%. Using the extraction solvent of1-undercanol withdensity lower than water and appropriate melting point near room temperature, thenovel DLLME-SFO were developed, in which the extraction solvent could easilycollected. Moreover, this method is more environmental-friendly than conventionalDLLME.However, the relatively high volume of the dispersive solvent, such as methanol oracetonitrile, could lead to a decrease in the partition coefficient of analytes. Thesecond experiment of this paper used surfactant as emulsifier, instead of conventionalunenvironmental-friendly dispersive solvent. This novel, simple and efficient SA-SFO-DLLME technique coupled with HPLC was developed for the determinationof three organophosphorus pesticides in tea samples, including parathion,methyl-parathion, and phoxim. Some parameters that affect the extraction efficiency,such as type and volume of extraction solvent and dispersive solvent, salt effect andpH were investigated and optimized in a5mL sample system by HPLC. The3pesticides were detected at275nm. Under the optimum conditions(extraction solvent:35μL of undecanol; dispersive solvent:0.216mmol/L of TritonX-100). Theexperimental data had a good characteristic of linearity in the range of1~200ng/mL,and the correlation coefficients (r) were from0.9948to0.9955; the relative standarddeviations (RSD) varied from9.7%to14.5%; the limits of detection (LOD) were0.22~0.28ng/mL; the enrichment factors (EF) varied from115.8to133.6; and therecovery ration in the real tea samples were from70.4%to102.1%. The proposedmethod could be used to analyse pesticide in different tea samples. |
