Copper(II)-selective potentiometric sensors based on porphyrins in PVC matrix

Cu 2+ selective sensors have been fabricated from polyvinyl chloride (PVC) matrix membranes containing neutral carrier porphyrin ( A and B) ionophores. The addition of sodium tetraphenylborate and the plasticizer DOP has been found to substantially improve the performance of the sensors. The membranes of various compositions of the two porphyrins were investigated and it was found that the best performance was obtained for the membrane of composition B:PVC:NaTPB:DOP in the ratio 5:150:2:150. The sensor shows a linear potential response for Cu 2+ over a wide concentration range 4.4 × 10 −6 to 1.0 × 10 −1 M with Nernstian compliance (29.3 mV decade −1 of activity) between pH 2.8 and 7.9 and a fast response time of ∼8 s. The potentiometric selectivity coefficient values as determined by fixed interference method indicate excellent selectivity for Cu 2+ ions over interfering cations. The sensor exhibits adequate shelf life (∼4 months) with good reproducibility (standard deviation ± 0.2 mV). The sensor can also be used in partially non-aqueous media having up to 20% (v/v) methanol, ethanol or acetone content with no significant change in the value of slope or working concentration range. The sensor has been used in the potentiometric titration of Cu 2+ with EDTA. The utility of the sensor has been tested by determining copper in vegetable foliar and swimming pool water sample successfully.