Methods and systems for monitoring electrolyte bath fluids are provided. The electrolyte bath fluids can be electroplating, electroless plating or etching solutions. The monitoring systems employ microfluidic devices, which have built in microfluidic channels and microfabricated thin-film electrodes. The devices are configured with fluid pumps to control the movement and mixing of test fluids through the microfluidic channels. The microfabricated thin-film electrodes are configured so that the plating or etching bath fluid composition can be characterized by electrochemical measurements. The monitoring methods and system provide faster measurement times, generate minimal waste, and occupy dramatically reduced physical space compared to conventional bath-monitor systems. The monitoring systems and method also provide low-cost system and methods for measuring or monitoring electroless plating bath rates.