Abstract: There is presented a porous unit (1) for detection of an analyte (96) in a liquid (99) by optical probing, comprising a translucent element (2) with a front side (3), and a backside (4) facing away from the front side (3), wherein the front side (3) is adapted for being contacted directly with the liquid (99), or separated from the liquid (99), such as exclusively separated from the liquid (99), by one or more layers at the front side (3) of the translucent element (2), the one or more layers (5) being adapted to be non-reflective to light reaching the one or more layers at least at one angle of incidence, such as at least at normal incidence, from the translucent element (2), and/or allow internal reflection, such as total internal reflection, at an interface, such as an external interface, of light reaching the interface from the translucent element (2), wherein the translucent element (2) comprises pores (6), wherein the pores (6) are dead end pores (6) extending from respective openings (7) fluidically co

Abstract: Processes for preparing ion selective membranes are presented which have selectivity for a primary analyte (in particular magnesium) as well as another ion (in particular calcium), wherein said process comprises addition of a) an ionophore (in particular 1,10-phenanthroline), b) a lipophilic salt containing said primary analyte (in particular hemi-magnesium bis[4-octylphenyl]phosphate) and c) a lipophilic salt containing said other ion (in particular hemi-calcium bis[4-octylphenyl]phosphate). Also, ion selective membranes are presented which are prepared using said processes, in particular to membranes selective for magnesium ions. In further aspects, electrodes and potentiometric sensors are presented comprising such membranes and the use thereof for determining ion concentrations in samples.

Abstract: Magnesium ion selective electrode membranes and the preparation thereof. The membranes are rendered highly selective for magnesium ions by the addition of acidic groups to the preferably PVC membrane, either by introducing a lipophilic compound comprising an acidic group covalently linked to a C4-C18 alkyl-substituted phenyl group (e.g. bis-4-octylphenyl phosphoric acid) into the membrane comprising the magnesium selective ionophore (e.g. a neutral ionophore 1,10-phenanthroline derivative) or by covalently linking an acidic (e.g. a carboxylic) group to the ionophore (e.g. a 1,10- phenanthroline derivative).