A digital microfluidic interface between solid-phase microextraction and liquid chromatography–mass spectrometry

•Solid-phase microextraction (SPME) and HPLC coupled with digital microfluidics.•Analytes extracted into a SPME were collected into a desorption droplet with automated digital microfluidic actuation.•Preconcentration of analytes was achieved because of the low volume of desorption solvent.•The method was applied to the quantitation of steroid hormones in human urine.

We introduce a method to couple solid-phase microextraction (SPME) with HPLC-MS using digital microfluidics (DMF). In the new system, SPME fibers are used to extract analytes from complex sample solutions, after which the analytes are desorbed into solvent droplets in a DMF device. The open geometry of DMF allows straightforward insertion of SPME fibers without requiring a complicated interface, and automated droplet manipulation enables multiplexed processing of the fibers. In contrast to other multiplexed SPME elution interfaces, the low volumes inherent to DMF allow for pre-concentration of analytes prior to analysis. The new SPME-DMF-HPLC-MS method was applied to the quantification of pg/mL-level free steroid hormones in urine. We propose that this new method will be useful for a wide range of applications requiring cleanup and pre-concentration with convenient coupling to high-performance analytical techniques.