Improved potassium-selective membrane using valinomycin as ionophore for ion-selective microdevices

Ion-selective field effect transistors (ISFETs) were tested for their suita bility for clinical work. They were intended for use in the analysis of blo od and serum, where the concentration of specific ions, e.g. sodium and pot assium, is of critical importance. The optical sensitivity of ISFETs and a new membrane composition for use in the clinical chemistry were evaluated. ISFETs with a polyimide/valinomycin membrane were shown to operate satisfac torily in the presence of proteins, encouraging the further development of these ISFETs as clinical sensors. ETH 2041 (tetra-n-undecyl 3,3', 4,4'-benz ophenone tetracarboxylate) and DGD (diethylene dibenzoate) were the plastic izers used and their performances were compared. Valinomycin was used as io nophore. The membranes were calibrated using the dip (solutions in the 10(- 1)-10(-5) mol dm(-3) KO range) and the constant volume dilution methods. Bo th membrane compositions gave good Nernstian responses. The ETH 2041 plasti cizer was found to yield devices more selective to potassium ion than the m ore easily usable DGD. (C) 2001 Elsevier Science B.V. All rights reserved.