Determination of organic peroxides in reversed micelles with a poly-N-methylpyrrole horseradish peroxidase amperometric biosensor

The preparation of a peroxidase biosensor by immobilization of the enzyme d uring the electropolymerization of N-methylpyrrole and its use in the deter mination of organic peroxides in a predominantly nonaqueous medium, such as reversed micelles, is reported. Reversed micelles were formed with ethyl a cetate as the continuous phase, 4% of 0.05 mol l(-1) phosphate buffer solut ion of pH 7.4 as the dispersed phase, and 0.1 mol l(-1) AOT as the emulsify ing agent. Working variables affecting the polymer biosensor preparation, s uch as the polymerization potential, the constant accumulated charge to sto p the polymerization process, the concentration of monomer and enzyme in th e polymerization solution and the pH and concentration of the phosphate buf fer solution, were optimized and discussed. Concerning the variables regard ing the amperometric measurements in the reversed micellar medium, the pote ntial value applied, the pH of the phosphate buffer solution, and the tempe rature were also optimized. Under the optimized conditions, the steady-stat e current for 2-butanone peroxide is reached in only 4 s. Linear calibratio n plots over the ranges 5-85 mu mol l(-1), and 2-48 mmol l(-1) were obtaine d for 2-butanone peroxide and tert-butylhydroperoxide, respectively. The li mits of detection obtained were 0.086 mu mol l(-1), and 0.03 mmol l(-1), re spectively. The poly-N-methylpyrrole-HRP amperometric biosensor was used fo r the determination of the organic peroxide content in body lotion samples, by employing 2-butanone peroxide as a standard. Optimization of the peroxi de extraction step from the sample was carried out, and recoveries approxim ating 100% were obtained. (C) 2001 Elsevier Science B.V. All rights reserve d.