Abstract: The design, construction and operation are described of a flow-through amperometric cell with a small Pt-wire working electrode and sub µL geometric volume and wherein the counter, working and reference electrodes are electrolytically connected by means of a Nafion solid polymer electrolyte. The cell was tested in a flow injection system with use of quinolin-8-ol (I), 4-methylcatechol (II) and K4Fe(CN)6 as model analytes. Calibration graphs were rectilinear from 0.2 to 0.6 µM up to 100 µM. In the determination of I at the 10 and 100 µM levels the coefficient of variation were 4.3 and 1.1% respectively (n = 10). Electrode activity decreased by 10 to 15% during a day's use but this could be restored by cyclic polarization of the working electrode between +1.6 and -0.2 V (vs. Ag - AgCl) for 15 min at 50 mV s-1. The detector has been applied in the HPLC determination of I, catechol and II on a Separon SGX C-18 column (15 cm x 3 mm) with aqueous 4% dioxan as mobile phase. AB An amperometric cell with a small platinum wire working electrode, a submicroliter geometric volume, and a solid polymer electrolyte (Nafion) was constructed and tested. The cell permits sensitive and reliable detection even in mobile phases of negligible elec. conductivity, (e.g., distilled water or nonpolar organic solvents). The sensitivity is substantially higher than that attained with similar cells containing large-area working electrodes; typical limits of detection amt. to analyte concentrations. between 10^-7 and 10^-6 mol/L, corresponding to subnanogram amounts in common HPLC sample volumes The detector response exhibits satisfactory linearity, a linear dynamic range of at least three concentration. decades, and a good precision, with relative standard deviations of 1 to 5%. This cell substantially widens the possibilities of amperometric detection, permitting direct application, for example, to normal-phase HPLC or to methods with programmed composition of the mobile phase (gradient elution).