ultrasonic and cooling approaches for reinforcement of the microextraction methods

since solid-phase and liquid-phase microextraction (spme and lpme) were introduced, as effective solvent-free methods, many efforts have been made to improve their modes and applications. however, due to limitations with sensitivity and efficiency, researchers have focused on improving the performance of their basic primary modes. in this way, in recent years, different methods such as ultrasonic-assisted microextraction (ua-me), microwave-assisted microextraction (ma-me), solvent-assisted microextraction (sa-me) and cooling-assisted microextraction (ca-me) were developed to reinforce the efficiency of the spme and lpme methods. these strategies make the microextraction methods more effective and applicable, to different sample matrices. in this article ua-me and ca-me, as the most important methods to enhance the efficiency of spme and lpme, were reviewed and their different aspects were evaluated and compared. comparison of different microextraction reinforcement approaches revealed that the ca-me is the most effective method to increase the extraction efficiency, especially for the analysis of complicated solid matrices.