Determination of Seven Pyrethroid Pesticides in Liquid Milk by Dispersive Liquid-Liquid Microextraction Based on the Solidification of a Floating Organic Droplet Followed by GC

A simple, rapid, and environmentally friendly method has been developed for the determination of seven pyrethroid pesticides in liquid milk by dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet coupled with GC. Several variables that affect the extraction efficiency, including the type and volume of the extraction solvent and those of the dispersing solvent, the extraction time, and the mass fraction of salt were optimized. Under the optimum conditions, good linearity was observed between 1.0 and 500.0 mu g L-1, with regression analysis yielding an r value (correlation coefficient) of > 0.9990 for the determination of the seven pyrethroid pesticides in liquid milk. The recoveries of the target analytes from liquid milk at spiking levels of 5.0, 10.0, and 20.0 mu g L-1 were between 90.2 and 108.4%. LODs for the analytes were 0.08-0.44 mu g L-1, while LOQs were 0.24-1.47 mu g L-1. The intraday (n = 6) and interday (n = 3) RSDs were less than 5.2 and 7.5%, respectively. The proposed method was successfully applied to determine the seven pyrethroid pesticides in real liquid milk.