Rapid Sample Preparation Using Slug Flow–Laminar Flow: Passive In Situ Microextraction/Stripping Coupling

To increase the detection accuracy of radioactive samples, sample preparation through liquid–liquid extraction (LLE) before instrumental analysis is a crucial step. LLE preparation involves multiple steps including the tedious separation steps of co-extraction and stripping, which may cause sample loss, radioactive contamination, and radioactive leaks. In this study, a novel hybrid slug flow–laminar flow (SFLF) microchip in passive mode was designed to couple extraction and stripping in situ to realize a one-step sample preparation. The difficulty in maintaining stable water–organic–water interfaces was mitigated by using a partition wall and three resistance isolation areas. The mass transfer performance of the SFLF microchip was investigated and compared with that of the supported liquid membrane and three-layer laminar flow microextraction/stripping systems. Furthermore, the applicability of the SFLF system in preparing radioactive samples was validated through the selective separation of Ce and Pr from Cs and Sr. The novel SFLF microextraction/stripping system has a stable flow pattern, high mass transfer efficiency, and superior operating flexibility.