Target factor analysis (TFA) has been used successfully with reaction data to determine, without knowledge of reaction kinetics, the number of independent reactions and the corresponding stoichiometries. This paper analyzes the applicability of TFA techniques to reaction data on the basis of concentration measurements. It is shown that, in some cases, a data matrix that is well suited to existing TFA techniques can be constructed from concentration measurements, material exchange terms, and initial conditions (data pre-treatment). Otherwise, TFA needs to be performed directly on the measured concentration data. In the latter scenario, knowledge of reaction-invariant relationships is required to specify necessary and sufficient conditions for the acceptance of stoichiometric targets. The case of unmeasured species is also investigated.