A simple procedure for the development of a range of polymeric ion-selective electrodes (ISEs) with low detection limits is presented. The electrodes were prepared by using a plasticizer-free methyl methacrylate-decyl methacrylate copolymer as membrane matrix and poly(3-octylthiophene) as intermediate layer deposited by solvent casting on gold sputtered copper electrodes as a solid inner contact. Five different electrodes were developed for Ag+, Pb2+, Ca2+, K+, and I-, with detection limits mostly in the nanomolar range. In this work, the lowest detection limits reported thus far with solid contact ISEs for the detection of silver (2.0 x 10(-9) M), potassium (10(-7) M), and iodide (10(-8) M) are presented. The developed electrodes exhibited a good response time and excellent reproducibility.