Combined headspace single-drop microextraction and solid-phase microextraction for the determination of phenols as their methyl ethers by gas chromatography-mass spectrometry

Combined SDME and SPME worked as an elegant strategy to inject a large sampled mass of analytes into a GC. After headspace SDME of methyl derivatives of phenol, chlorophenols, methylphenols and other substituted phenols into 10 mu L of solvent drop (1-butanol), the extract was subjected to headspace SPME (DVB/CAR/PDMS, 30/50 mu m, fiber) for convenient transfer of analytes to the fiber and then into the GC. This combination resulted in achieving a high sensitivity of detection for a small volume (0.5-2 mL) of sample. The chromatographic separation of thirteen model phenols (as their methyl ethers) was complete within 10 min. A rectilinear calibration graph was obtained using combined headspace SDME/SPME and GC-MS in the range of 0.001-5 mg L-1, with a correlation coefficient of 0.990-0.999 and an average limit of detection of 20 ng L-1 (range 8-45 ng L-1), which was far better than that obtained by headspace SDME, 90 ng L-1 (range 50-138 ng L-1), or headspace SPME, 55 ng L-1 (range 36-70 ng L-1), when used alone. In spiking experiments on environmental water samples, the RSD of the results was in the range of 4.6-9.4%.