A low-cost battery-powered amperometric detector for Flow Injection Analysis and High Performance Liquid Chromatography has been developed. The potentiostat is controlled by a personal computer through an 8 bit Analog-to-Digital, Digital-to-Analog card. The electronic design of the potentiostat is based on high-gain low-power operational amplifiers. This configuration allowed us to use batteries as the power source, minimizing power source noise.