Ion-selective electrodes, which detect activity of specific substances, are one of main analytical techniques in many fields e.g. medical and environmental analysis or process control in industries. This article describes manufacturing of screen-printed electrode for potassium determination, which can be used in potentiometric measurements. Electrode was made with usage of two conductive pastes. The first consists of silver nanoplatelets and thermoplastic polyurethane (TPU). The second contained PMMA matrix and graphene nanoplatelets as intermediate material. Two membranes for electrode coating, which differ in composition, were prepared and compared. For both membranes polyvinyl chloride (PVC) was used as a matrix and valinomycin was used as ionophore which binds potassium ions. Moreover, some of the prepared electrodes had an additional intermediate layer made of a conductive polymer - poly(3,4-ethylene-1,4- dioxythiophene) (PEDOT). Received calibration curves were linear. The curve slope for electrode with PEDOT intermediate layer in the physiological range (3,8-5,5 mM) was 62 mV/dec which exceed the Nernstian value.