Kinetic Spectrophotometric Determination of N-acetylcysteine ethyl Ester using Bichinchoninic Acid

N-acetylcysteine ethyl ester (NACET) according to reported data has the potential to substitute NAC as a mucolytic agent, as a paracetamol antidote and as a glutathione related antioxidant. NACET once it is administered quickly enters the cells where it is transformed to NAC and cysteine. A novel kinetic spectrophotometric method of analysis is developed for the determination of NACET with the use of Bicinchoninic acid (2-(4-Carboxyquinolin-2-yl)quinoline-4-carboxylic acid, BCA), a highly sensitive and specific reagent for Cu+-ions. The proposed method is based on a reduction reaction of a Cu(BCA)22+ complex by NACET to a purple Cu(BCA)2+ complex in a phosphate buffer solution. The absorbance of the generated complex is measured at 562 nm. The parameters optimized included: pH of the reaction solution, the effect of temperature, the molar ratio of Cu2+/NACET, the molar ratio of BCA/NACET and the molar ratio of Cu2+/BCA. The effect of interfering substances was also investigated. A fixed time method was utilized for the construction of a linear calibration graph from 4.0×10–7 to 1.0×10–4 mol L–1 of NACET by the use of the kinetic spectrophotometric method where the detection limit was 1.6×10–7 mol L–1.