Chemiluminescence determination of dopamine using N, P-graphene quantum dots after preconcentration on magnetic...

A novel sorbent consisting of magnetic oxidized nanocelluloses modified with graphene quantum dots was prepared and used for the separation and preconcentration of dopamine. The eluted dopamine from the sorbent was determined by a designed chemiluminescence system containing luminol, H₂O₂, Fe³⁺, and graphene quantum dots doped with nitrogen and phosphorus. Graphene quantum dots cause an increase in the intensity of the chemiluminescence system of luminol-H₂O₂, but the presence of Fe³⁺ ions in this system decreases its intensity because of the sorption of the Fe³⁺ ions on the surface of P, N-graphene quantum dots. However, the addition of dopamine resulted in the retrieval of P, N-graphene quantum dots, as well as the chemiluminescence intensity, due to the formation of its complex with Fe³⁺. The sorbent made of magnetic oxidized nanocelluloses modified with graphene quantum dots was characterized by various analytical techniques, and the effective parameters on the extraction of dopamine were investigated and optimized. Under the optimized conditions, the method displayed good linearity in the concentration range 0.25-17.5 µg L^-1 for dopamine (R² = 0.9918) with a limit of detection of 0.054 µg L^-1. The intra- and inter-day relative standard deviations at a 10.0 µg L^-1 concentration level of dopamine (n = 6) were 2.6 and 4.1%, respectively. This method was successfully applied to the extraction and determination of dopamine in human serum and urine samples.