A new method for low mercury concentration analysis in drinking waters is presented. Membranes containing a few micrograms of various complexing reagents were produced on the surface of quartz glasses (reflectors). The reflectors were immersed in water solutions containing various concentrations of inorganic mercury salts at low concentrations (1-40 ng/mL). The membranes were left to equilibrate in 5-500 mL of solution for many hours; when the equilibration stage was finished they were cleaned with ultrapure water and left to dry. Analyses were performed by total reflection X-ray fluorescence (TXRF). The effects of various experimental parameters (complexing agent, equilibrium time, sample volume, etc.) as well as the selectivity of the membranes were studied. The complexing reagent dithizone with a PVC-based membrane gave the best results. The limit of quantitation was 0.8 ng/mL.