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　(similar　to　75　mu　m　id).　A　cathodic　EOF　of　similar　to　3.3　x　10(-4)　cm(2)　V-1　S-1　was　maintained　using　sodium　polystyrene　sulfonate　(PSSNa)　with　a　molecular　weight　of　5　x　10(5)　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　50s　and　theoretical　plate　numbers　of　8.0　x　10(5)/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.　(C)　2016　Elsevier　B.V.　All　rights　reserved.