The construction of an electrochemical detector flow cell for high-performance liquid chromatography from stainless steel, which also serves as the auxiliary electrode, is described. Glassy carbon is used for the working electrode in a novel configuration based on a hybrid of the wall-jet and thin-layer arrangements. Application of the detector to the determination of morphine in small blood samples is described. The metabolite, morphine-3-glucuronide, is also determined by hydrolysis with beta-glucoronidase prior to extraction. The detector is capable of detecting less than 1 ng of morphine injected.