[en] This paper describes synthesis and characterization of radioactive gold nanoparticles ("1"9"8Au-NPs), and explores their utility as a radiotracer for tracing an aqueous phase in a continuous laboratory-scale bubble column at ambient conditions. The performance of the "1"9"8Au-NPs as a radiotracer was compared with the results obtained with a conventional radiotracer i.e. bromine-82 ("8"2Br) as ammonium bromide and found to be identical. A tank-in-series with backmixing model (TISBM) was used to simulate the RTDs of the aqueous phase and characterize flow in the bubble column. - Highlights: • "1"9"8Au-NPs were used as radiotracer for tracing aqueous phase. • The RTD of the aqueous phase was measured using "1"9"8Au-NPs and "8"2Br radiotracers. • The performance of "1"9"8Au-NPs as radiotracer was compared and validated. • Tank-in-series with backmixing model was used to simulate the measured RTDs.