Polyetheretherketone (PEEK)-based open tubular ion chromatography for perchlorate detection

Open tubular ion chromatography (OTIC) offers a lightweight, low-pressure and efficient platform for on-site ion analysis. Polyetheretherketone (PEEK) is an attractive column substrate because of its mechanical strength, chemical resistance and thermal stability, yet conventional sulfuric-acid sulfonation limits ion-exchange capacity and requires long preparation times. Here, a mixed methanesulfonic and sulfuric acid reagent followed by acetone rinsing was used to streamline the sulfonation process, producing a roughened inner surface with higher functional group density. The optimized 25 μm i.d. PEEK capillaries achieved a cation-exchange capacity of 2.5 ± 0.1 peq/mm², roughly eight times higher than that from single-acid treatment. The latex-coated columns had an anion-exchange capacity of 20.0 ± 0.8 peq/mm² and enabled baseline separation of perchlorate within 5 min using 6 mM sodium salicylate as the eluent. When integrated with a nonsuppressed OTIC system and electromembrane extraction, the method exhibited high reproducibility (RSD < 3%), a quantitation limit of 0.2 μM, and recoveries of 87.6-114.9% in environmental samples, confirming its reliability and sensitivity for perchlorate analysis.