ELECTROANALYTICAL DETERMINATION OF CODEINE IN PHARMACEUTICAL PREPARATIONS

ABSTRACT

A square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC) using a glassy carbon electrode were evaluated for the determination of codeine in pharmaceutical preparations. The interference of several compounds, such as acetaminophen, guaiacol, parabens, ephedrine, acetylsalicylic acid and caffeine, that usually appear associated with codeine pharmaceutical preparations was studied. It was verified that these electroanalytical methods could not be used with acetaminophen present in the formulations and that with guaiacol, parabens or ephedrine present the use of the FIA-EC system was impracticable. A detection limit of 5 µmol L⁻¹ and a linear calibration range from 40 to 140 µmol L⁻¹ was obtained with the SWV method. For the flow injection analysis procedure a linear calibration range was obtained from 7 to 50 µmol L⁻¹ with a detection limit of 3 µmol L⁻¹ and the FIA-EC system allowed a sampling rate of 115 samples per hour. The results obtained by the two methods, SWV and FIA-EC, were compared with those obtained using reference methods and demonstrated good agreement, with relative deviations lower than 4%.

Keywords:

• Codeine
• Square wave voltammetry
• Flow injection analysis with electrochemical detection
• Acetaminophen
• Guaiacol
• Parabens
• Ephedrine
• Acetylsalicylic acid
• Caffeine

ACKNOWLEDGMENTS

One of us (J. M. P. J. G.) would like to thank the PRODEP Program Ph.D. grant. We would like to thank Ms. Iris Van Den Steen for her help with some of the routine work. We also wish to thank M. J. Paiva and M. Lima for their help.