Pyridinemonocarboxylate ion selective electrodes

A heterogenous solid-membrane electrode with Cu nicotinate as the active component and a liq.-membrane electrode with nicotinic acid ester (cetyl nicotinate) as the active component were prepd. and used to det. nicotinate ion concn.  The calibration curves were linear for 5 × 10-4-5 × 10-2 and 1 × 10-4-5 × 10-1 M nicotinic acid by using the solid and liq. membranes, resp.  The solid-membrane electrode gave also a linear response to Cu concn. in the range 7 × 10-3-5 × 10-1 M.  The solid-membrane electrode was characterized by better mech. properties and a more stable signal.  The liq.-membrane electrode was characterized by a higher selectivity.