Vortex solvent bar microextraction for phthalate esters from aqueous matrices.

An improved hollow fiber solvent bar microextraction method termed as vortex solvent bar microextraction (VSBME) was developed. A short hollow fiber immobilized with organic extraction solvent was served as the solvent bar for microextraction of phthalate esters from aqueous matrices. The hydrophobic analytes were pre-focused at the bottom of the vortex under the vigorous magnetic stirring before extraction, which facilitated the mass transfer of analytes from aqueous matrix to organic extraction phase in the subsequent solvent bar microextraction. With the extraction solvent lost gradually from the hollow fiber under the stirring, the efficient extraction was maintained by the absorption of analytes in the porous membrane. After extraction, the analytes were desorbed from the hollow fiber membrane using 50 μL organic solvent. The phthalate esters with 1-octanol/water partition coefficients ranging from 1.69 to 8.83 were used as model compounds to investigate the extraction performance. Extraction conditions such as type and volume of extraction solvents, stirring intensity, extraction time, sample concentration and volume were investigated and optimized. Analysis was carried out with gas chromatography-mass spectrometry (GC-MS). Under the optimum conditions, this new method gave super high enrichment factors (over 1500), good reproducibility (<7.1%, n=6) in a rapid extraction within 5 min. It allowed the determination of phthalate esters at ng L(-1) level. Compared with the other microextraction methods, the proposed VSBME was simpler, more robust and had higher enrichment efficiency. The matrix effects on the extraction performance were also investigated with bottled ice red tea, red wine and human urine.