An all thiol-ene microchip for solid phase extraction featuring an in situ polymerized monolith and integrated 3D replica-molded emitter for direct electrospray mass spectrometry

摘要

Pre-concentration and clean-up are essential sample preparation steps in environmental, forensics and bio-analytical assays. Here, we present work towards a fully integrated, replica molded all thiol-ene lab-on-a-chip solution for sample enrichment and mass spectrometry. A microfluidic chip based column, for solid phase extraction (SPE), was fabricated using thiol-ene as both bulk material and an in situ polymerized monolith. C-11-alkyl chains, in the form of undecanethiol, could be directly immobilized at the monolith surface, through the thiol-ene click reaction. Capacity of the produced SPE columns, for the test compound anthracene, was investigated by UV/Vis absorbance by connecting the chips to the detector of a commercial CE instrument with the help of a 3D-printed chip holder. The column capacity for anthracene was found to be ca. 14 mu g m(-2), which is consistent with the surface density of functional groups present at the monolith surface. The SPE column was further integrated with a unique on-chip electrospray ionization (ESI) emitter and hyphenated to an ion trap mass spectrometer. The emitter is directly replica molded in the process of chip fabrication, without any additional post-processing, and features a three-dimensional taper. The produced electrospray was investigated in the range of 250-370 m/z and found to be stable with a relative standard deviation of 8 +/- 3%. Using the endogenous steroid progesterone, on-line extraction was also investigated on the SPE-ESI chip by direct infusion. Recoveries ranging from 40-50% indicated that further work is required to improve performance. However, the potential of an all-polymer, inexpensive device for sample clean-up featuring an integrated ESI emitter opens up an array of possibilities for applications in fields where single-use devices are mandatory, such as medical, biological, and pharmaceutical applications.