Rational construction of an electrophoretic system for the determination of flaxseed lignans by capillary...

A rational strategy was developed for constructing a capillary electrophoretic system for the separation of structurally related flaxseed lignans. Electrophoretic selectivity was sequentially optimized through background electrolyte composition, dynamic capillary modification, and organic modifier content using multivariate experimental design. The selected system consisted of 20 mmol L^-1 borate, 7.5 mmol L^-1 phosphate, and 2.5 mmol L^-1 citrate (pH 11.0), containing 0.20% (w/v) PDADMAC and 20% (v/v) methanol, with separation at -20 kV. The method separated pinoresinol, lariciresinol, matairesinol, secoisolariciresinol, and secoisolariciresinol diglucoside. Quantitative validation was established for secoisolariciresinol and secoisolariciresinol diglucoside, determined at 0.87 ± 0.05 mg g^-1 after sequential alkaline-acid hydrolysis and 6.6 ± 0.3 mg g^-1 after alkaline hydrolysis, respectively. Field-amplified sample injection was additionally explored for improving detectability, although signal enhancement was accompanied by loss of selectivity for the lariciresinol-matairesinol pair.