PPb level monitoring of lanthanium by a novel PCV-membrane sensor based on 4-methyl-2-hydrazinobenzothiazole

A novel poly(vinyl chloride) (PVC)-based membrane sensor for lanthanum ions was prepared by employing 4-methyl-2-hydrazinobenzothiazole (MHBT) as an ionophore, sodium tetraphenyl borate (NaTPB) as an anion excluder, and dibutylphthalate (DBP), acetophenon (AP) and nitrobenzene (NB) as plasticizing solvent mediators and investigated as a selective membrane sensor.The best performance was observed with a membrane having a composition of PVC:MHBT:DBP:NaTPB = 30:6:61:3 in the concentration range of 1.0 × 10−7 to 1.0 × 10−1 M La3+. The sensor exhibited a Nernstian slope of 19.8 mV per decade in La3+ activity. The detection limit of the sensor was 2.5 × 10−8 M (∼3.8 ppb). The proposed electrode showed the excellent discriminating ability toward La3+ ions with regard to most alkali, alkaline earth, transition and heavy metal ions. It was successfully applied to the determination of lanthanum in two mouth wash preparations. The sensor was also used as an indicator electrode in the potentiometric titration of lanthanum ions with an EDTA solution.