A strategy to modulate the electrophoretic behavior in plastic microchips using sodium polystyrene sulfonate

•PSSNa was used as BGE for the electrophoresis on COC microchips.•Strong and stable cathodic EOF was obtained in COC microchips.•PSSNa also acted as viscosity regulator, surface modifier, pseudostationary phase.•Unique morphology of PSSNa offered an extra factor to affect resolution.•The proposed method was used for rapid analysis of biogenic amines in fish meat.

Plastic microchips have been broadly used as disposable microfluidic devices, but the poorly defined surface properties limit their application. Herein, we proved that an anionic polymer could be used as the background electrolyte (BGE) to provide a strong and stable cathodic electroosmotic flow (EOF) and modulate the electrophoretic behavior for efficient separation in relative thicker microchannels (∼75 μm id). A cathodic EOF of ∼3.3 × 10−4 cm2 V−1 s−1 was maintained using sodium polystyrene sulfonate (PSSNa) with a molecular weight of 5 × 105 as the BGE, which ensured fluorescein isothiocyanate labeled biogenic amines (BAs) appeared ahead of other components in the electropherograms obtained with microchips of cyclic olefin copolymer. Four selected BAs appeared within 50 s and theoretical plate numbers of 8.0 × 105/m were achieved. The role of PSSNa was evaluated with streaming potential, dynamic light scattering, contact angle and atomic force microscopy. Its functionalities as surface modifier, viscosity regulator and pseudostationary phase were also confirmed. The proposed electrophoretic method was applied in the fast determination of BAs in fish meat samples.