As an experimental complement to FFMD simulation, neutron diffraction with isotopic substitution (NDIS) can provide invaluable insight into structural correlations in aqueous solutions. By leveraging the distinct scattering properties of isotopes, NDIS isolates specific atomic interactions with minimal perturbation to the system. This is achieved by preparing isotopically substituted yet chemically identical solutions and subtracting their scattering profiles to isolate contributions from the substituted nucleus, thus enabling sub-angstrom resolution. This study integrates FFMD and NDIS to investigate TMA-pyridine cation-π interactions. The high solubility of pyridine in water makes NDIS experiments feasible, with the potential to establish benchmark data not only for the present case but also for modeling biologically relevant cation-π interactions involving TMA with also other aromatic molecules such as phenol or indole.