Novel Ion Selective Electrodes for Determination of Lisinopril: A Study of Plasma and Plasma Proteins Effect.

Three l isinopril-selective electrodes were developed with different techniques and in different polymeric matrices. Precipitation based technique with bathophenanthroline-ferrous as cationic exchanger in polyvinyl chloride (PVC) was used for the fabrication of sensor I (classical electrode) and sensor II (coated wire electrode). Hydroxypropyl s cyclodextrin-based techniques were used for the fabrication of sensor III using tecoflex (graphite electrode).Linear responses were obtained for the three sensors in the concentration ranges 10 -7 - 10 -4 M, 10 -6 - 10 - 3 M and 10 -6 - 10 -4 M with slopes of 36.6 2, 32.66 and - 50.37 mv/decade for sensors I , II and III; respectively. The average recoveries are of 99.75 ± 1.141 %, 99.51± 1.198% and 99.79 ± 1.261% for sensors I , II and III respectively The effect of pH and temperature were studied for the three sensors . The sensors show good selectivity to the drug in presence of a variety of inorganic and organic interferents including drugs of related substances. The proposed procedures were compared to the British pharmacopoeial method and showed no significant difference. The effect of serum levels of electrolytes (145 mmol/L Na + , 4.3 mmol/L K + and 1.26 mmol/L Ca 2+ ) was also studied and was found to be negligible. The behavior of all three sensors in presence of bovine serum albumin (BSA), globulins and human plasma was studied. The three sensors were then used to determine lisinopril in plasma with average recoveries of 88.45 ±1.284 %, 83.42 ± 1.6% and 99.64 ± 0.972 % for sensors I , II and III; respectively.