Analytical performance of cylindrical carbon fiber microelectrodes in low-permitivity organic solvents:: determination of vanillin in ethyl acetate

The electrochemical behavior of cylindrical carbon fiber microelectrodes (CFMEs), 8 mm in length, has been tested in low-permitivity organic solvents such as toluene and ethyl acetate. Near-to-ideal steady-state responses were obtained by cyclic voltammetry for ferrocene solutions in these media, using low potential scan rates and a relatively high concentration of background electrolyte. A good adjustment of the voltammetric responses to that predicted by the theory was found in both solvents. Welt-defined oxidation peaks were also obtained by differential-pulse and square wave voltammetry. Square-wave voltammetry (SWV) in ethyl acetate has been used to develop a method for the determination of the food additive vanillin. A linear calibration graph was obtained in the 1.0x10(-5) to 7.0x10(-4) mol l(-1) concentration range with a slope of (7.1+/-0.1)x10(3) mu A l mol(-1). A limit of detection of 4.2x10(-6) mol l(-1) vanillin, and a relative standard deviation of 2.0% for a concentration level of 5.0x10(-4) mol l(-1) (n=10) were obtained. The SWV method was applied to the determination of vanillin in dehydrated pudding powder. This determination was performed directly in the samples extract in ethyl acetate. The obtained results were statistically compared with those provided by a reference spectrophotometric method, and no significant differences between both methods were found. (C) 1999 Elsevier Science B.V. All rights reserved.