Preparation and characterization of alkyl methacrylate-based monolithic columns for capillary gas chromatography applications

• Preparation of methacrylate monolithic capillary columns for gas chromatographic applications.
• Characterization of the prepared monoliths.
• Evaluation of the hydrodynamic properties and separate a model alkanes and alkyl benzenes samples.
• Investigate the resolution and efficiency, as well as a comparison with an open tubular conventional column.
• Evaluate the repeatability, reproducibility and stability of the prepared columns and separate a gasoline sample.

Gas chromatography (GC) is considered the least common application of both polymer and silica-based monolithic columns. This study describes the fabrication of alkyl methacrylate monolithic materials for use as stationary phases in capillary gas chromatography. Following the deactivation of the capillary surface with 3-(trimethoxysilyl)propyl methacrylate (TMSM), the monoliths were formed by the co-polymerization of either hexyl methacrylate (HMA) or lauryl methacrylate (LMA) with different percentage of ethylene glycol dimethacrylate (EDMA) in presence of an initiator (azobisisobutyronitrile, AIBN) and a mixture of porogens include 1-propanol, 1,4-butanediol and water. The monoliths were prepared in 500 mm length capillaries possessing inner diameters of 250 μm. The efficiencies of the monolithic columns for low molecular weight compounds significantly improved as the percentage of crosslinker was increased, because of the greater proportion of pores less than 50 nm. The columns containing lower percentages of crosslinker were able to rapidly separate a series of 8 alkane members in 0.7 min, but the separation was less efficient for the light alkanes. Columns prepared with the lauryl methacrylate monomer yielded a different morphology for the monolith-interconnected channels. The channels were more branched, which increased the separation time, and unlike the other columns, allowed for temperature programming.