Copper(II) phthalocyanine as an electrocatalytic electrode for cathodic detection of urinary tryptophan

Herein, we introduce a novel method for tryptophan detection via a reduction reaction facilitated by its interaction with a copper(II) phthalocyanine (CuPc) electrocatalytic electrode. This method addresses challenges associated with the susceptibility of the oxidation response to interference from various species when measuring tryptophan in bodily fluids. The reduction currents exhibit a linear increase with tryptophan concentrations in two ranges: 0.0013-0.10 mM and 0.10-1.20 mM, with the sensitivities of 14.7 ± 0.5 μA mM^-1 and 3.5 ± 0.1 μA mM^-1, respectively. The limit of detection (LOD, 3S_B/m) is determined to be 0.39 μM. The sensor exhibits excellent reproducibility, with the relative standard deviation of <5%. Application of the sensor to authentic urine samples yields a % recovery of 101 ± 4%.