“…Clearly, finding an apparently linear relationship between ln(intensity) and contact time [2,3,29,32,33,44,45,49,50,56] is not sufficient to guarantee that an accurate T 1r H value can be determined. Fitting an exponential decay function to the decay phase of VCT data [16,52], essentially an equivalent procedure, suffers from the same problem when slowly cross-polarizing nuclei are present. The VCT experiment will only give accurate T 1r H values when the absence of slowly cross-polarizing nuclei can be assured [46].…”