Capillary electrophoresis and electrospray ionization on a single-thread microfluidic system for rapid mass spectrometry detection

This study presents a novel microfluidic system using a single thread for sample loading, pinch focusing, sample separation and electrospray ionization (ESI) for rapid mass spectrometry detection of liquid biosamples. Instead of using a physical channel for sample transportation, polyester thread of 200 μm in diameter is used as the liquid route such that delicate channel fabrication process can be excluded. With the opened liquid route, liquid sample is directly applied at arbitrary site of the thread for electrophoresis separation. Neighboring buffer drops are then used to pinching focus the sample plug to narrow the sample plug and enhance the separation performance. The tail end of the thread is then applied another high voltage for electrospray ionizing the electrophoresis separated samples for MS detection. Rapid sample detection can be achieved without time consuming chip fabrication and sample preparation processes. Results showed that the sample plug can be reduced about 70% of its original band width. The ESI can sustain stable for more than 30 min with a high ion intensity of 109 ions/cm3. The ingredients of commercial medicine of eye drops and energy drink of Red Bull are successfully detected using the developed scheme. The developed method provides a simple yet high efficient way for liquid chromatography mass spectrometry (LC-MS) detection of bio-samples in ambient.