Ion Selective Electrodes for Potentiometric Determination of Baclofen in Pharmaceutical Preparations

Two different sets of baclofen sensors were developed for its potentiometric determination in pharmaceutical preparations, based on the fact that baclofen behaves as cation in acidic medium and anion in basic medium (pK1=9.62 and pK2=3.87;respectively). Six baclofen- selective electrodes were investigated using precipitation based technique with either sodium tetraphenyl borate as an anionic exchanger or 1, 10-ortho-phenanthrolineferrous as a cationic exchanger; respectively upon using polyvinyl chloride (PVC) matrix and dioctylsebacate (DOS) as a plasticizer. The resultant sensors have different forms, either as membrane electrodes (sensors I&IV), coated wire electrodes (sensors II&V) or as microsized graphite electrodes (sensors III&VI). Linear responses of 10-6–10-2 M with slopes of 43.05, 43.11, and 43.05 mv/decade within pH range 4-6 were obtained for sensors I, II and III. On The other hand, Linear responses of 10-7–10-3 M with slopes of 55.90, 57.13 and 57.37 mV/decade within pH 6-8 range were obtained for sensors IV, V and VI; respectively.All these sensors were prepared and fully characterized in terms of composition, life span, usable pH range, response time and temperature. The sensors show good selectivity to the drug in presence of a variety of inorganic and organic interferent substances. The proposed procedures were compared to the USP pharmacopoeial method and showed no significant difference. The proposed sensors displayed useful analytical characteristics for the potentiometric determination of baclofen in pure form and in pharmaceutical preparations.