Preparation of MWCNT′s-SH/AuNP′s/ME and Its Application to Determination of Dopamine

Sulfhydryl multiwalled carbon nanotubes (MWCNT′s-SH) were prepared by the reaction of carboxy multiwalled carbon nanotubes (MWCNT′s-COOH) with sulfhydryl ethylamine. The MWCNT′s-SH was then added to a reaction mixture containing NaBH4 and HAuCl4, by which the gold nanoparticles (AuNP′s) produced were self-assembled onto MWCNT′s-SH and MWCNT′s-SH/AuNP′s powder was obtained. By pulverization and pressing of the MWCNT′s-SH/AuNP′s powder with the microelectrode (ME) to have the powder filled into the small hole at the top of ME, the modified MWCNT′s-SH/AuNP′s/ME was prepared. Electrochemical behavior of the modified electrode was studied by cyclic voltammetry. It was found that a pair of redox peaks given by dopamine was observed at the modified electrode. Linearity range for dopamine between 5.0×10-6 and 6.4×10-4mol·L-1 was obtained, with detection limit (3S/N) of 5.1×10-9mol·L-1. The proposed method was used in the determination of dopamine in injection samples, giving results in consistency with the labeled values. Recovery of the method was tested by standard addition method, giving recovery in the range of 98.0%-103.0%.