Determination of cysteamine using label-free gold nanoparticles

Label-free gold nanoparticles were applied as a colorimetric probe for the determination of cysteamine. The approach is based on aggregation of the nanoparticles leading to a change in the absorption spectra and color of the solution. The influence of different factors (the presence of EDTA, pH, the concentrations of cysteamine and the nanoparticles) on the aggregation and analytical performance of the procedure was investigated. The potentiality of EDTA as a masking agent to eliminate the interference of metal cations was estimated. The method allows the determination of cysteamine with a detection limit of 0.01 μg mL−1. It was applied to the analysis of a hair-waving formulation and urine.