Poly(2-amino-5-(4-pyridinyl)-1, 3, 4-thiadiazole) film modified electrode for the simultaneous determinations of dopamine, uric acid and nitrite

Poly(2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole) (PAPT) modified glassy carbon electrode (GCE) was fabricated and used for the simultaneous determinations of dopamine (DA), uric acid (UA) and nitrite (NO2 (-)) in 0.1 mol L-1 phosphate buffer solution (PBS, pH 5.0) by using cyclic voltammetry and differential pulse voltammetry (DPV) techniques. The results showed that the PAPT modified GCE (PAPT/GCE) not only exhibited electrocatalytic activities towards the oxidation of DA, UA and NO2 (-) but also could resolve the overlapped voltammetric signals of DA, UA and NO2 (-) at bare GCE into three strong and well-defined oxidation peaks with enhanced current responses. The peak potential separations are 130 mV for DA-UA and 380 mV for UA-NO2 (-) using DPV, which are large enough for the simultaneous determinations of DA, UA and NO2 (-). Under the optimal conditions, the anodic peak currents were correspondent linearly to the concentrations of DA, UA and NO2 (-) in the ranges of 0.95-380 mu mol L-1, 2.0-1,000 mu mol L-1 and 2.0-1,200 mu mol L-1 for DA, UA and NO2 (-), respectively. The correlation coefficients were 0.9989, 0.9970 and 0.9968, and the detection limits were 0.2, 0.35 and 0.6 mu mol L-1 for DA, UA and NO2 (-), respectively. In 0.1 mol L-1 PBS pH 5.0, the PAPT film exhibited good electrochemical activity, showing a surface-controlled electrode process with the apparent heterogeneous electron transfer rate constant (k (s)) of 25.9 s(-1) and the charge-transfer coefficient (alpha) of 0.49, and thus displayed the features of an electrocatalyst. Due to its high sensitivity, good selectivity and stability, the modified electrode had been successfully applied to the determination of analytes in serum and urine samples.