Nonionic surfactant dynamic coating of poly(dimethylsiloxane) channel surface for microchip electrophoresis of amino acids

The strong interactions between poly(dimethylsiloxane) (PDMS) surface and amino acids result in unavoidable adsorption on channel surface. This paper described a simple method to decrease adsorption of analytes by dynamic coating of the PDMS surface. When nonionic surfactant (Tween 20) was added in running buffer as dynamic modifier, electroosmotic flow (EOF) was well-suppressed. Moreover, arginine (Arg), proline (Pro), histidine (His) and threonine (Thr) were successfully separated within 80 s in a 3.7 cm long separation channel and then detected with an end-channel amperometric detection mode at a copper electrode. Under the optimal conditions, the linear ranges of Arg, Pro, His and Thr were all from 50 to 600 μM with detection limits of 13.6, 15.3, 10.6 and 12.8 μM, respectively. The relative standard deviations (R.S.D.s) of run-to-run, day-to-day and chip-to-chip on the coated PDMS/PDMS microchip were all below 2.4%. Tween 20 dynamic coating provides reproducible amino acids separations with good performances.