In order to characterise antibody binding characteristics it is necessary to determine reaction constants from quantitative measurements of the process. Surface plasmon resonance (SPR) provides convenient real-time measurement of the reaction that enables subsequent estimation of the reaction constants. Two models are considered that represent the binding reaction in the presence of transport effects. One of these models, the effective rate constant approximation, can be derived from the other applying a quasi-steady state assumption. Uniqueness of the reaction constants with respect to SPR measurements is considered via a structural identifiability analysis. It is shown that the effective rate constant model is unidentifiable, unless the analyte concentration is known, while the full model is structurally globally identifiable provided association and dissociation phases are considered. Both models provide comparable estimates for the unknown rate constants for a commercial anti-A monoclonal IgM experiment.