Double matrix membranes for potentiometric cation selective disposable sensors

The construction of double matrix membranes (DMM) for disposable NH ₄ ⁺ , Na⁺ and pH sensors is described. The usual polymer matrix membrane was incorporated in an inert micro fibre matrix (MFM). Capillary forces distribute the cocktail homogeneously in the MFM; this also determines the thickness. Sensors using the new DMM have shown selectivity, detection limits and slope comparable with polymer matrix membranes. The advantages of DMMs are their mechanical stability, the feasibility of low cost mass production with identical parameters and improved handling.