Combination of Solid Phase Extraction-Dispersive Liquid Liquid Microextraction and Pre-column Derivatization Method for Determination of Trace Level Estrogens in Water Sample
A method,carbon nanotubes assisted solid phase extraction combined with dispersive liquid-liquid microextration and pre-column derivatization(SPE-DLLME-PFD),was developed for the determination of estriol(E3),bisphenol A(BPA),17α-ethinyl estradiol(EE2) and 17β-estradiol(E2) in water samples.SPE,DLLME and PFD process was studied and optimized using central composite design and response surface plot.The optimized conditions were as follows: target estrogens were adsorbed from 210 mL aqueous samples into 30 mg carbon nanotubes at 2.0 mL/min;methanol used as elution solution was concentrated to a volume of 0.6 mL,which was mixed with 100 μL of C6MIM and the blend was added to 2.0 mL of deionized water(25.0% NaCl,g/L).After centrifugation,20 μL of the settled organic phase was mixed with 4.0 mg derivating agent,and the reaction was occurred for 25 min at 40 ℃.Finally,0.1 mL of methanol was used to dissolve the particles of derivating agent,and 20 μL of that sample was analyzed.Under the chosen conditions,linearity range of the established method was 0.05-5.00 μg/L with R2 of 0.9966-0.9999 for the target estrogens,and the LODs were in the range of 0.13-6.33 ng/L.The recoveries of estrogens under different spiked levels for four estrogens were 83.13%-122.39%(RSD was 1.7%-9.6%).E3 and BPA could be detected in the most of the real water samples.Compared with some other methods,the present method needed long extraction time,large volume sample and multi-steps,while it also had many advantages such as low LOD,simplicity of operation,and environmental friendly.