RESUMO
Two microextraction techniques--liquid phase microextraction based on solidification of a floating organic drop (LPME-SFO) and dispersive liquid-liquid microextraction combined with a solidification of a floating organic drop (DLLME-SFO)--are explored for benzene, toluene, ethylbenzene and o-xylene sampling and preconcentration. The investigation covers the effects of extraction solvent type, extraction and disperser solvents' volume, and the extraction time. For both techniques 1-undecanol containing n-heptane as internal standard was used as an extracting solvent. For DLLME-SFO acetone was used as a disperser solvent. The calibration curves for both techniques and for all the analytes were linear up to 10 microg/mL, correlation coefficients were in the range 0.997-0.998, enrichment factors were from 87 for benzene to 290 for o-xylene, detection limits were from 0.31 and 0.35 microg/L for benzene to 0.15 and 0.10 microg/L for o-xylene for LPME-SFO and DLLME-SFO, respectively. Repeatabilities of the results were acceptable with RSDs up to 12%. Being comparable with LPME-SFO in the analytical characteristics, DLLME-SFO is superior to LPME-SFO in the extraction time. A possibility to apply the proposed techniques for volatile aromatic hydrocarbons determination in tap water and snow was demonstrated.
