O2k-TPP+ ISE-Module: 2 potentiometric ion-selective electrodes (ISE), supported by the Oroboros O2k (O2k-Series D and higher). The ISE module is designed with replaceable membranes making it possible to measure different ions such as TPP+ or Ca2+ with the same electrode housing*. The main application of the O2k-TPP+ ISE-Module is measurement of mitochondrial membrane potential with tetraphenylphosphonium (TPP+) or TPMP+.
*There are other ion selective membranes available (e.g., from Sigma Aldrich), for a wide variety of ionic species. If cut to a circle with a diameter of 4 mm these membranes can be used in the ISE system. Many ions may also be detected by fluorimetric based methods.