Novel Green Potentiometric Method for the Determination of Lidocaine Hydrochloride and its Metabolite 2, 6‐Dimethylaniline; Application to Pharmaceutical Dosage Form and Milk

Sustainable chemistry has attracted the attention of scientists during the last decades owing to the great advantages encountered by its application. These include: waste reduction, energy conservation and substitution of hazardous substances with more eco‐friendly ones. Following this approach, a new sensitive and selective membrane sensor was developed and investigated for the determination of lidocaine hydrochloride (LD) and its carcinogenic metabolite 2,6‐dimethylaniline (DMA). Several polyvinyl chloride (PVC) based sensors were tried using different plasticizers as well as different cation exchangers. The best response was achieved upon using dioctylphthalate (DOP) as solvent mediator and phosphotungstate (PT) as cation exchanger. LD was selectively determined at pH 6 without interference from its carcinogenic metabolite, while DMA that had been reported to be the toxic inactive metabolite of LD secreted in the milk was determined in the milk at pH 2. Fast, stable Nernstian responses were achieved by the proposed sensors over a concentration range of 2.66×10−5 M to 1×10−2 M for both LD and DMA. The method was validated according to the IUPAC recommendations and was successfully applied for the determination of LD in pure form and pharmaceutical dosage form, whereas DMA was successfully determined in pure form and spiked milk samples.