Dispersive liquid–liquid extraction based on magnetic Pickering emulsion followed by gas chromatography–tandem mass spectrometry for the simultaneous determination of aldehydes in environmental water samples

A dispersive liquid–liquid extraction based on Pickering emulsion stabilized with ferroferric oxide grafted nitrogen-doped graphitized carbon black has been developed to simultaneously determine seven aldehydes in environmental water samples, in combination with pentafluorobenzyl hydroxylamine precolumn derivatization gas chromatography–tandem mass spectrometry. The nitrogen-doped graphitized carbon was prepared from dicyandiamide waste residue with a simple acid wash process. The effects of magnetic emulsifier amount, extraction time, solution pH, and oil/water volume ratio on the formation of magnetically responsive Pickering emulsion and the extraction efficiency of the proposed dispersive liquid–liquid extraction were also investigated. Under the optimized conditions, satisfactory linearities were obtained for all aldehydes with correlation coefficients larger than 0.9984. The limits of detection and quantitation of seven aldehydes were in the range of 17.3–30.1 ng/L and 54.3–103.4 ng/L, respectively, with intra- and interday relative standard deviations less than 8.6%. The mean recoveries at three spiked levels ranged from 70.0 to 101.4%. With the Pickering emulsion as a “minimized extractor”, the extraction was accomplished within 5 min. After extraction, the magnetic disperser could be recovered for reuse at least five times by an external magnetic field. The proposed method was demonstrated to be feasible, simple, and economic for the trace analysis of the aldehydes in environmental water samples.