Voltammetric determination of epinephrine with a 3-mercaptopropionic acid self-assembled monolayer modified gold electrode

Epinephrine (EP) could exhibit an anodic peak at a bare gold electrode, but it was very insensitive. However, when the bare gold electrode was modified with 3-mercaptopropionic acid (3MPA) self-assembled monolayer (3MPA SAM), the peaks of EP became more reversible and sensitive due to the accumulation and mediate efficiency of 3MPA SAM. Conditions such as solution pH, concentration of supporting electrolyte and accumulation time were optimized. Under the selected conditions (i.e., 0.02 M pH 6.8 sodium phosphate buffer, accumulation time: 2 min under open-circuit.), the height of the anodic peak at about 0.18 V (vs. SCE) was linear to EP concentration in the range of 2 x 10(-7) - 1 x 10(-6) M and 1 x 10(-6) - 5 x 10(-4) M with correlation coefficient of 0.995 and 0.999, respectively. When the 3MPA/Au was further modified with cysteamine, the interference of H2O2 and BTO3- was eliminated. But the resulting electrode still suffered from the interference of ascorbic acid. This method was used to determine the content of EP in adrenaline hydrochloride injections, and the recovery was in the range of 97.0% to 105.1%.