Polyallylamine-coated capillary electrophoresis with capacitively coupled contactless conductivity detection for rapid analysis of functional anions in bread

Abstract

Background: This study introduces a polyallylamine (PAA)-coated capillary electrophoresis (CE) method combined with capacitively coupled contactless conductivity detection (C⁴D) for the rapid and efficient separation of anions in bread. This approach utilizes suppressed cathodic electroosmotic flow (EOF) for improved separation performance. In contrast to conventional reversed - EOF methods that depend on dynamic cetyltrimethylammonium bromide (CTAB) coatings, which require long equilibration times and result in peak drift, this work utilizes a stable, covalently grafted PAA coating achieved through 3-glycidoxypropyltrimethoxysilane. This stable coating effectively regulates cathodic EOF, producing more reliable and reproducible separation results. Results: Polyallylamine-coated capillary surface achieves a stable and significantly reduced cathodic electroosmotic flow (EOF), improving separation efficiency. The plate number (N) 0.4 × 10⁵ - 0.9 × 10⁵ m⁻¹, while resolution is enhanced, enabling the quantification of 20 anions within a shortened separation time (∼10 min), thereby improving the overall performance of the method. This method also demonstrated excellent reproducibility, with %RSD of relative migration time (RMT) < 0.5 %. This is a notable advancement over conventional reversed EOF methods, which typically experience higher variation. The system's EOF mobility, efficiency (plate number and resolution), precision, and long-term surface stability with over 80 consecutive runs were thoroughly validated. Thereby confirms the robustness and repeatability of the technique for applications, particularly in complex matrices such as bread analysis. Significance: This coating approach enables stable and reproducible CE-C⁴D analysis of anions with a capillary coated with 0.01 % PAA reagent. The covalently bonded PAA suppresses cathodic EOF, eliminates buffer additives, and ensures consistent migration times over 80 separation cycles. Compared with conventional CTAB coatings, the PAA-coated capillary offers higher stability, improved sensitivity with larger peak areas, and enhanced reproducibility, enabling identification of 20 anions in bread samples within ∼10 min for high-throughput food analysis.