Simultaneous online enrichment and identification of trace species based on microfluidic droplets.

A facile online enrichment protocol has been proposed based on microfluidic droplets acting as an interface between a liquid chromatography separation system and detection systems of ESI-MS/MS and laser-induced fluorescence. Low-abundance species were successfully concentrated and analyzed in this system via droplet shrinkage. The proposed platform significantly increased the enrichment efficiency and detection sensitivity with reduced sample handling steps, short analysis time, and no cross-contamination. The presented system is universal, shows no discrimination, and is easily coupled with other separation and detection approaches.