Aminoglycoside antibiotics(AMGs),a class of amino-containing carbohydrates,are widely used in therapy against bacterial infections.Due to their high polarity and short of chromophores,analysis of these drugs is inconvenient by common HPLC and GC,whereas they are in accordance with separated by capillary electrophoresis and monitored by electrochemical detection.The electrophoretical separation of AMGs is likely to be achieved under acidic medium due to their positively charged amino groups.However,the electrochemical detection of these compounds on metal electrode generally requires a strongly alkaline condition.Herein,we improve a typical microfluidic chip with ability to adjust pH through two branch channels hydrostatically pushing alkaline solution into a W-shape mixing channel with acidic medium from separation channel.As a result,the pH increases to high value required for electrochemical detection of AMGs.The application of this method has been demonstrated by analysis of six AMGs in biological samples.