Molybdate sensor based on 5,10,15,20-tetraphenylporphyrinatocobalt complex in a PVC matrix

Poly(vinyl chloride) (PVC) based membranes of 5,10,15,20-tetraphenylporphyrinatocobalt, ( I ), incorporating dibutyl phthalate (DBP) in the composition 9:55:36 ( I :PVC:DBP) responds to molybdate (MoO 2− 4 ) over the concentration range 7.6×10 −6 –1.0×10 −1 mol l −1 , pH between 4.9 and 11.3, with a Nernstian slope and a fast response time of 15 s. The membrane shows excellent selectivity towards MoO 2− 4 ions over a number of other anions and exhibits stable response for more than four months. The sensor can be used in non-aqueous medium with no significant change in the value of slope or working concentration range for the estimation of MoO 2− 4 in solutions having upto 25% (v/v) non-aqueous fraction. It was applied for the estimation of molybdenum as molybdate in a sample of molybdenite, a low grade ore.