Dispersive liquid–liquid microextraction method based on solidification of floating organic drop combined with gas chromatography with electron-capture or mass spectrometry detection

A simple dispersive liquid–liquid microextraction (DLLME) method based on solidification of a floating organic drop (DLLME-SFO) technique combined with gas chromatography/electron-capture detection (GC/ECD) or gas chromatography/mass spectrometry (GC/MS) has been developed. The proposed method is simple, low in cost, and of high precision. It overcomes the most important problem in DLLME, the high-toxic solvent used. Halogenated organic compounds (HOCs) in water samples were determined as the model compounds. The parameters optimized for the DLLME-SFO technique were as follows: A mixture of 0.5 mL acetone, containing 10 μL 2-dodecanol (2-DD-OH), was rapidly injected by syringe into the 5 mL water sample. After centrifugation, the fine 2-DD-OH droplets (8 ± 0.5 μL) were floated at the top of the screwcap test tube. The test tube was then cooled in an ice bath. After 5 min the 2-DD-OH solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and 3 μL (for GC/ECD) or 2 μL (for GC/MS) of it was injected into a gas chromatograph for analysis. The limit of detection (LOD) for this technique was 0.005–0.05 μg L−1 for GC/ECD and was 0.005–0.047 μg L−1 for GC/MS, respectively. The linear range of the calibration curve of DLLME-SFO was from 0.01 to 500 μg L−1 with a coefficient of estimation (r2) > 0.996 for GC/ECD and was from 0.02 to 500 μg L−1 with a coefficient of estimation (r2) > 0.996 for GC/MS.