High Efficient Extraction of Phthalates in Aquatic Products by a Modified QuEChERS Method

A simple, environmentally friendly and high efficient extraction method was proposed for the determina- tion of five phthalates in aquatic products by gas chromatography combined with mass spectrometry detector （GC-MS）. When this method was adopted, samples were pretreated by modified QuEChERS（quick, easy, cheap, effective, rugged and safe） method. An environmentally friendly extractant（ethanol aqueous solution） replaced toxic acetonitrile for extracting phthalates in the protein-matrix samples. Fluorescence quenching spectra of bovine serum albumin（BSA） with phthalates show that there was a high-affinity interaction between phthalate and protein, de- creasing the extraction efficiency of phthalates from fish samples. However, in the 80%（volume fraction, ~） ethanol aqueous solution, a slow but full protein denaturation takes place, which would cause the unfolding of protein and the release of phthalates. Meanwhile, the fat-soluble impurities are extracted less in ^（ethanol） 80% aqueous solution than in either ~p（ethanol） 100% or hydrophobic solvents in the liquid-liquid extraction procedure. Therefore the puri- fication steps were greatly simplified. Overall recoveries were 81.77%--90.5% with limits of detection between 2.53 and 9.61 ~tg/L, and relative standard deviation values at 1.15%---4.85%. The proposed approach was satisfactorily applied to the determination of phthalates in real aquatic products, such as fish, shrimp and oyster.

Rapid determination of pesticide residues in Chinese materia medica using QuEChERS sample preparation followed by gas chromatography-mass spectrometry

Pesticide residue analysis plays an important role in the quality control of Chinese materia medica.This paper reports the development and validation of an analytical method for the quantitative determination of the residues of 39 pesticides in 12 different matrices of Chinese materia medica.Sample preparation utilized the QuEChERS method with acetonitrile:1% aqueous acetic acid(9:1,v/v)as extraction solvent followed by sample clean-up by dispersive solid phase extraction using primary secondary amine sorbent and graphitized carbon black.Extracts were then analysed by gas chromatography coupled with electron impact mass spectrometry in the selected ion monitoring mode.Limit of detection(LOD)and limit of quantitation(LOQ)values were in the ranges 0.5-50 ng/g and 1-100 ng/g,respectively.The recoveries of the 39 pesticides were in the range 75-112% with precision(as relative standard deviation,RSD)<15%.The results show that the modified QuEChERS method allows rapid and sensitive analysis of multiple pesticide residues in Chinese materia medica.