Reshaping of pipette tip: A facile and practical strategy for sorbent packing-free solid phase extraction

Pipette tip-based solid phase extraction (PT-SPE) has been proved to be an effective and user-friendly separation technique due to its miniaturized procedure and practical convenience. However, the vast majority of existing PT-SPE devices consist of a filter-sorbents-filter sandwich structure, which may suffer the unforeseen risk of sorbents leakage caused by the looseness of filters. More importantly, many high-capacity nanosorbents with particle size smaller than pore size of filters are unavailable. Thus, sorbent packing-free and sample low-consumption PT-SPE could be a more robust strategy for separation and detection, but such a possibility has not been explored yet. Herein we report a tubing reshaping strategy for facile fabrication of sorbent packing-free PT-SPE devices. Three types of reshaped PTs, namely stretched tube-like, self-crimping and filter in-built PTs, were fabricated via simple heating and stretching operations. The reshaped PTs exhibited flexible surface chemical post-modification. The SPE process was directly performed in reshaped PTs with an obviously enhanced extraction efficiency compared to once-shaping PTs while no need of packing sorbents. Extraction of nucleosides from human urine by boronic acid-functionalized reshaped PTs was demonstrated. Our findings technically renovate the structural composition of PT-SPE devices. As PTs are inexpensive and high-plasticity, the sorbent packing-free SPE scheme presented herein could find more promising applications and provides a new perspective for design and fabrication of novel sorbent packing-free SPE devices.