Simultaneous colorimetric determination of dopamine and ascorbic acid based on the surface plasmon resonance band of colloidal silver nanoparticles using artificial neural networks

Abstract

A new method for simultaneous determination of dopamine (DA) and ascorbic acid (ASC) is proposed. The method is based on the reaction of dopamine and ascorbic acid with the oxidizing agent (silver nitrate) in the presence of PVP (as a stabilizer) and the formation of silver nanoparticles in a slightly basic medium. Spectrophotometry is used to monitor the changes of the surface plasmon resonance (SPR) band at a maximum wavelength of silver nanoparticles (440 nm) vs. time. Three-layered feed-forward artificial neural networks (ANN) trained by back propagation learning algorithm is used to model the relationship between absorbance and concentration to quantify analyte in mixtures under optimum conditions. Sigmoidal and linear transfer functions were used in the hidden and output layers, respectively. Linear calibration graphs were obtained in the concentration range of (3.2 × 10⁻⁶ – 2.0 × 10⁻⁵ mol L⁻¹) for DA and (2.0 × 10⁻⁶ – 4.8 × 10⁻⁵mol L⁻¹) for ASC. The detection limits were 8.0 × 10⁻⁷ and 6.2 × 10⁻⁷ mol L⁻¹ for DA and ASC, respectively, which are comparable by different spectrophotometric and colorimetric methods. The method was applied successfully to the determination of dopamine (DA) and ascorbic acid in human serum samples.