Lanthanum(III) Ion Selective Electrode Based on a New Ionophore

A PVC membrane electrode based on 1-[({[(butylsulfunyl)carbothioyl]disulfanyl} carbothioyl)sulfanyl]butane as a suitable ion carrier for determination of lanthanum(III) ion was prepared. This electrode revealedsuch a good selectivity toward La3+ ion over a wide variety of other metal ions. Some experimental parametersuch as membrane composition, nature, and amount of plasticizer, the amount of additive, and concentrationof internal solution on the potential response of La3+ sensor were investigated. The electrode exhibits aNernstian slope of 20.9±1.8 mV per decade of La3+ over a wide concentration range 3.3×10-7-1.0×10-2 M inthe pH range 3.7-7.3. The response time is about 7s and detection limit is 2.5 ×10-7 M and it can be used forat least 1month without any considerable divergence in potential. It was used as an indicator electrode inpotentiometric titration of lanthanum(III) ion with EDTA.