Preparation of monolithic polymer columns with homogeneous structure via photoinitiated thiol-yne click polymerization and their application in separation of small molecules.

Abstract

Two monolithic polymer columns were directly prepared in the UV-transparent fused-silica capillaries via photoinitiated thiol-yne click polymerization of 1,7-octadiyne (ODY) with a dithiol (1,6-hexanedithiol, 2SH) or a tetrathiol (pentaerythriol tetrakis(3-mercaptopropionate), 4SH) within 15 min. The rapid polymerization provided a time-saving approach to optimize preparation conditions. Then, two porogenic systems of diethylene glycol diethyl ether (DEGDE)/tetrahydrofuran (THF) and DEGDE/poly(ethylene glycol) (PEG, Mn = 200) were found to effectively control the porous structure of two kinds of polymeric monoliths (O2SH and O4SH), respectively. The almost disappearance of thiol and alkynyl vibrations (2560 and 2115 cm(-1), respectively) in infrared spectra and Raman spectra indicated a high conversion of the thiol-yne polymerization reaction. The thiol-yne polymerization was further proved by analyzing the energy-dispersive X-ray spectrum (EDS), MALDI-TOF mass spectrum, and elemental data. Scanning electron microscopy (SEM) images showed the monolithic polymer columns with homogeneous porous structure and macropore size of 0.5-1.0 μm, which facilitated the minimum plate heights of 10.0-12.0 μm for alkylbenzenes in reversed-phase liquid chromatography (RPLC). The low values of the A and C terms (<1.0 μm and <15.5 ms, respectively) in the van Deemter equation were similar to those obtained by some monolithic silica columns. The BSA tryptic digest was also separated on the monolithic polymer column by cLC-MS/MS. The result with 85% protein coverage was better than those given by some hybrid monolithic columns. The monolithic polymer columns were further applied for separation of phenols, natural products, and standard proteins and demonstrated satisfactory separation ability.