The solid-state 13C cross-polarization magic angle spinning nuclear
magnetic resonance (CPMAS-NMR) spectra of crystalline tetracycline
and tetracycline-loaded zeolite beta were acquired using
a CPMAS-NMR instrument (AVANCE III, 400 MHz, Bruker,
Germany) with a 4 mm H/X/Y. The main experimental parameters
included contact time of 3 ms, pulse delay of 1 s, spinning rate