A carbon paste electrode modified with a cobalt(II) coordination polymer for the direct voltammetric determination of tryptophan

We have synthesized a cobalt(II) coordination polymer and have characterized it by various methods including X-ray single crystal structural analysis. The polymer was used as modifier to fabricate a carbon paste electrode that displays electrochemical activity towards tryptophan (Trp). Trp is oxidized at the surface of the electrode in buffer solution of pH 4.2, yielding a single peak at 814 mV. The experimental conditions such as the concentration, the composition and the pH values of the supporting electrolyte, accumulation time, and the scan rate were optimized. Under the optimized conditions, the current of peak is linearly related to the concentration of Trp in the range from 0.2 to 8.0 mu M, and from 8.0 to 80.0 mu M. The detection limit (at S/N = 3) is 0.1 mu M at an accumulation time of 60 s. The determination of Trp in amino acid injection solutions was evaluated and the results were satisfactory. The recoveries were in the range of 97.5% to 103.0%.