Centrifugeless dispersive liquid-liquid microextraction based on salting-out phenomenon as an efficient method for determination of phenolic compounds in environmental samples

A new centrifugeless dispersive liquid-liquid microextraction (DLLME) method was applied for the convenient extraction of some phenolic compounds from environmental samples. After dispersing the extracting solvent into the sample solution (10.0 mL), the mixture was passed through a small column filled with 5 g sodium chloride. As a result, phase separation was achieved via the salting-out phenomenon, and the extracting solvent was suspended on top of the sample solution. Using a low-toxic and solidifiable extracting solvent (1-dodecanol), after immersing the column into an ice bath, the extracting solvent was solidified, collected easily, and injected into an HPLC-UV instrument. The overall extraction time was 7 min, consumption of the extracting solvent was efficiently reduced to 50 mu L, and the centrifugation step was simply eliminated, which made the automation of the procedure easier than the normal DLLME technique. A series of parameters influencing the extraction were investigated systematically. The optimal experimental conditions were found to be 50 mu L of 1-dodecanol as the extracting solvent, a flow rate of 2.0 mL min(-1), and a pH value of 4.0 for the sample solution. Under these conditions, the method provided a good linearity in the range of 0.5800 ng mL(-1), low limits of detection (0.1-0.3 ng mL(-1)), good extraction repeatabilities (RSDs below 9.1%, n = 5), and enrichment factors of 100-160.