Abstract
Polymers are interesting housing materials for the fabrication of inexpensive monolithic chromatography and solid phase extraction (SPE) devices. Challenges arise when polymeric monoliths are formed in non-conical, cylindrical tubes of larger diameter due to potential monolith detachment from the housing wall resulting in loss of separation performance and mechanical stability. Here, a two-step protocol is applied to ensure formation of robust homogeneous methacrylate monolith in polypropylene (PP) tubing with a diameter of 2.0 mm. Detailed Fourier-transform infrared (FTIR) spectroscopic analysis and Scanning Electron Microscopy (SEM) imaging confirm the successful pre-modification of the tubing wall with an anchoring layer of cross-linked ethylene dimethacrylate (EDMA). Subsequent formation of an EDMA-glycidyl methacrylate (GMA) monolith in the PP tube resulted in a homogeneous monolithic polymer with enhanced mechanical stability as compared to non-anchored monoliths.
Highlights
Over the past two decades, polymer monoliths have found many applications, broadly subdivided between chromatographic/electrophoretic separations and sample preparation in the form of solid phase extraction (SPE)
Conventional commodity PP tubing from ink pens was used as housing material
The device manufacture scheme is presented in Figure 1; after ink removal and tubing cleaning a three-step process was performed
Summary
Over the past two decades, polymer monoliths have found many applications, broadly subdivided between chromatographic/electrophoretic separations and sample preparation in the form of solid phase extraction (SPE). A key challenge in these systems is to prevent monolith detachment from the housing wall due to the shrinkage during the monolith polymerization step, as that would negatively impact the separation performance and possibly the mechanical stability of the monolith. The risk of wall detachment increases with increasing housing diameter. In the vast majority of cases, monoliths are formed within fused silica capillaries (diameter < 300 μm) due to their facile covalent attachment to the wall via prior vinylization of the silica surface using reagents such as 3-(trimethoxysilyl)propyl methacrylate [1]. When a plastic housing, such as polypropylene (PP) or cyclic olefin copolymer (COC), is used the surface attachment to the housing is somewhat more challenging due to the hydrophobicity and low reactivity of polyolefines
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