Ion Selective Membrane Electrodes for Stability Indicating Determination of Benoxinate Hydrochloride in Pure form and in Drug Product

This paper presents a comparative study between four sensors constructed to determine benoxinate hydrochloride (BX) in the presence of its hydrolysis induced degradation product using different ion association complexes and plasticizers. Precipitation based technique was used for sensors fabrication. The BX complexes with the cationic exchangers; BX- reinikate, BX-tetraphenylborate, BX-phosphotungestate, and BXtetrakis were obtained in situ by soaking the PVC membranes in 1×10-2 BX solution. Dioctylphthalate and nitrophenyl octyl ether were used as solvent mediators. The proposed sensors showed fast, stable Nernstian responses across a relatively wide BX concentration range (5×10-5 to 10-1 M) in the pH range of 4-6. The suggested sensors could be used for several weeks without any measurable change in sensitivity. They displayed good selectivity for BX in presence of its degradation product, common inorganic and organic species. The proposed sensors were successfully applied for the determination of BX in pure powder form and eye drops where good recoveries were obtained.