Voltammetric determination of dopamine at a zirconium phosphated silica gel modified carbon paste electrode

Zirconium phosphated amorphous silica gel (devoted briefly as Si–ZrPH) modified carbon paste electrode (CPE) was used for detection of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). Cyclic voltammetry demonstrated improved reversibility of the DA on the modified electrode. Cyclic voltammetry of Fe(CN)63−/4− as a negatively charged probe revealed that the surface of the Si–ZrPH modified CPE surface had a high density of negative charge. As a result, the modified carbon paste electrode could inhibit the voltammetric response of AA and UA while the redox reaction of dopamine was promoted. Based on this, a selective method has been developed to detect DA in the presence of 2500 and 1000 time higher concentration of AA and UA, respectively. The effect of various experimental parameters on the voltammetric response of dopamine was investigated. Under the chosen conditions, the differential pulse voltammetry peak current was found to be linear with DA concentration in the ranges of 0.04 to 50 µM and 50 to 400 µM. The detection limit of the proposed method in the presence of 100 µM of AA and 40 µM of UA was found to be 0.02 µM for DA determination. Satisfying results are achieved when detecting the DA in injection and human serum samples.