Simultaneous determination of tartrazine, sunset yellow and allura red in foods using a new cobalt-decorated carbon paste electrode

A simple, sensitive and economical sensor based on carbon paste decorated with a cobalt complex (Co_C/CPE) was developed and applied to the simultaneous detection of pairs of synthetic dyes most commonly used in foods, which are tartrazine-sunset yellow (TZ-SY) and tartrazine-allurared (TZ-AR). Micro composite surfaces were characterized by electrochemical impedance spectroscopy (EIS). Anodic peak currents for TZ-SY and TZ-AR as a function of pH, Co_C concentration, time and adsorption potential were observed at 1.0–0.79 V and 1.0–0.81 V, respectively, by CV. In addition, the increase in the anodic peak currents was greater than 100% for TZ-SY and TZ-AR using the carbon paste decorated with the Co(II) complex. The detection limits were 0.30 × 10⁻⁶ - 0.90 × 10⁻⁶ mol L⁻¹ for the TZ-SY pair and 0.8 × 10⁻⁷-0.37 × 10⁻⁶ mol L⁻¹ for the TZ-AR pair. The new method was validated with a standard of unflavored gelatin spiked with small amounts of TZ-SY and TZ-AR and showed a recovery percentage greater than 90%. Finally, the versatility of the sensor was applied in foods such as orange and strawberry flavored gelatin, powdered, soft drinks and pharmaceutical dosages. The statistical study showed that this method is equally reproducible, stable and accurate compared to other previously reported methods.