Determination of Nitrite in Meat Products using a Metalloporphyrin Based Nitrite-Selective Membrane Electrode
Vlascici Dana, Pica Elena Maria, Fagadar-Cosma Eugenia, Bizerea Otilia, Cosma Viorica
The potentiometric response characteristics of a nitrite-selective electrode based on Co (III) tetraphenylporphyrins (TPP) in o-nitrophenyloctylether plasticized polyvinyl chloride membranes are compared. To establish the optimum composition of the membrane, different molar percents of cationic derivative (0-100 mol% relative to ionophore) were used. The influence of different plasticizers: o-nitrophenyloctylether, dioctylphtalate and tricresilphosphate on potentiometric answer were studied. Electrodes formulated with membranes containing 1 wt% ClCoTPP, 66 wt% o-NPOE, 33 wt% PVC (plasticizer:PVC = 2:1) and the lipophilic cationic derivative (10 mol%) are shown to exhibit high selectivity for nitrite over many anions, except the lipophilic anions perchlorate and thiocyanate. The electrodes based on Co (III) porphyrins were used for the potentiometric determination of nitrites in meat products. The results were compared with a colorimetric method used as the reference method. There was a good agreement between the potentiometric and colorimetric procedures.