Electrochemical synthesis of a novel thiazole-based copolymer and its use for the simultaneous determination of dopamine, uric acid and nitrite

A poly(2-amino-4-thiazoleacetic acid-co-3-amino-5-mercapto-1,2,4-triazole) (PATA-AMT) film modified glassy carbon electrode (GCE) has been fabricated by using electrochemical copolymerization of 2-amino-4-thiazoleacetic acid (ATA) and 3-amino-5-mercapto-1,2,4-triazole (AMT) and used for electro-catalytic oxidations of dopamine (DA), uric acid (UA) and nitrite ion (NO2−) in 0.1 mol L−1 phosphate buffer solution (PBS, pH 6.0). The surface morphology of the copolythiazole film has been investigated by using scanning electron microscope (SEM). The SEM images show the formation of a non-periodic nano-network structure with a diameter of the fibril varying over the range of 55–85 nm. The copolythiazole film (PATA-AMT) modified GCE (PATA-AMT/GCE) not only exhibits strong electro-catalytic activities toward oxidations of DA, UA and NO2− with negatively shifted oxidation overpotentials and enhanced peak current responses, but also can resolve the sluggish and overlapped voltammetric waves of DA, UA and NO2− into three sensitive and well-defined oxidation peaks by both cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which can be applied for the selective and simultaneous determinations of DA, UA and NO2− in a mixture. Under the optimum conditions, the linear concentration dependences of the DPV current responses are observed for DA, UA and NO2− in the concentration ranges of 0.85–390 μmol L−1, 1.95–1200 μmol L−1 and 2.0–1240 μmol L−1 with the correlation coefficients of 0.9993, 0.9993 and 0.9977, respectively. The detection limits are 0.2 μmol L−1, 0.25 μmol L−1 and 0.5 μmol L−1 for DA, UA and NO2−, respectively (S/N = 3). The different electrochemical behaviors of DA, UA and NO2− at various scan rates indicate that the electrode reaction of DA is an adsorption-controlled process, and those of UA and NO2− are diffusion-controlled processes at PATA-AMT/GCE. The practical application of the modified electrode has been investigated by the simultaneous determinations of DA, UA and NO2− in human urine and serum samples by using standard adding method with satisfactory results.