A quantitative method to analyze labeled S spin systems is proposed. Different from non-labeled systems, the reciprocity relation is broken down in labeled systems by residual S spins dipole-dipole interactions and indirect interactions. But under fast MAS, these interactions are reduced considerably and demand a longer time to communicate between different parts of the Hamiltonian. Therefore within a short contact time (<0.5 ms), the same quantitative method can be used for both non-labeled and labeled systems. The method is independent of local structures and can be applied to samples of multiple substances. (C) 2014 Elsevier By. All rights reserved.