Miniaturization of Liquid-Liquid extraction; the barriers and the enablers

Liquid-phase microextraction (LPME) is an important technique of sample preparation that has been widely applied for the extraction of different organic, inorganic and pharmaceutical compounds from different environmental and biological matrices. The low consumption of organic solvents, simplicity, speed, flexibility, and cheapness are all merits that encouraged scientists to the continuous development of LPME. There are three liquid-phase microextraction configurations, including single drop microextraction, hollow-fibre liquid-phase microextraction, and dispersive liquid–liquid microextraction. Each mode has several modalities that overcame the limitations of others. The continuous developments and modifications aim to achieve better extraction efficiency in a short time with simple technical procedures. This review discusses the principle and the applications of each mode, focusing on the barriers and the enablers for the development of new modalities.