Channel wall coating on a poly‐(methyl methacrylate) CE microchip by thermal immobilization of a cellulose derivative for size‐based protein separation

We demonstrate channel wall coating using a cellulose derivative on a poly‐(methyl methacrylate) (PMMA) CE microchip to eliminate EOF disturbing protein separation. The channel walls were modified by preconditioning with a solution containing the cellulose derivative and then thermally evaporating the solution to produce hydrophilic channel walls which prevent adsorption of analytes via a hydrophobic interaction. When the PMMA substrate was coated with the cellulose derivative hydroxypropylmethylcellulose (HPMC) 90SH, the water contact angle on the coated substrate was decreased (up to 15°) and EOF was significantly suppressed (up to 4.0×10 −6  cm 2 ⋅V –1 ⋅s –1 ). Three proteins (20.5, 68.0, and 114.6 kDa) were successfully separated on the 0.15% HPMC 90SH‐coated channel walls with good reproducibility of migration time (RSD <1.75%) and high efficiency (theoretical plate number per meter: 2.62×10 5 ).