Iron(III) ionophores based on formylsalicylic acid derivatives as sensors for ion-selective electrodes

Novel iron(III)-selective PVC membrane electrodes based on formylsalicylic acid derivatives were studied. The electrode based on p-chloroaniline-3-for mylsalicylic acid as a sensor, containing potassium tetrakis(4-chlorophenyl )borate as a lipophilic salt and o-nitrophenyl octyl ether as a plasticizer , gave the best performance. The electrode exhibits a good Nernstian respon se for 10(-1)-5.0 x 10(-5) mol l(-1) FeCl3 with a slope of 20 mV per decade . It shows a high selectivity for iron(III) in comparison with alkali, alka line earth and heavy metal ions. The electrode response and selectivity rem ained almost unchanged for at least 1 month. The effects of plasticizers, m embrane supports, lipophilic salts and pH on the potential response of the electrode were also studied. The electrode was successfully applied to the determination of iron(III) contents in some rocks.