Functionalization of High-Density Polyethylene Capillaries for Open Tubular Ion Chromatography

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Ion chromatography is a standard for anion analysis.
• Miniaturized Open Tubular Ion Chromatography (OTIC) offers efficient ion separations.
• Fabricating functionalized capillaries for OTIC presents challenges.

Purpose of the Study:

• To fabricate and characterize high-density polyethylene (HDPE) open tubular anion exchange columns (OTCs) for efficient OTIC.
• To explore methods for functionalizing HDPE capillary bores for anion exchange.
• To evaluate the performance and stability of fabricated OTCs.

Main Methods:

• Functionalization of HDPE capillary bores via sulfonation (chlorosulfonic or sulfuric acid) with or without prior grafting.
• Attachment of positively charged latex particles to create anion exchange sites.
• Measurement of ion exchange capacity and separation abilities.
• Analysis of column degradation using high-resolution mass spectrometry.

Main Results:

• Successful fabrication of HDPE OTCs by attaching latex particles to functionalized capillary surfaces.
• Exploration of sulfonation and grafting techniques for bore functionalization.
• Observed gradual loss of ion exchange capacity in many columns.
• Identified leaching of oxidized/sulfonated fragments as a cause of column degradation and latex site poisoning.

Conclusions:

• HDPE OTCs can be fabricated for OTIC, but column stability and longevity are significant challenges.
• Sulfonation and grafting methods require optimization to prevent leaching and maintain performance.
• Further research is needed to ameliorate degradation and rejuvenate columns for sustained anion analysis.