Rotary resonance methods

A new scheme for heteronuclear decoupling, phase-inverted supercycled sequence for attenuation of rotary resonance (PISSARRO), designed for fast MAS has been reported. " Its efficiency compares favourably with CW, TPPM, SPINAL and XiX decoupling methods at medium and high rf amplitudes, particularly under conditions where the efficiency of decoupling is affected by undesired rotary resonance effects. 

Preparative HPLC is another convenient method for isolating degradants from excipient compatibility matrices (72,73). The peaks from stressed samples can be collected, the solvent removed with a rotary evaporator, and the remaining solution lyophilized to obtain purified compounds. The samples can then be analyzed by other methods such as mass spectrometry and nuclear magnetic resonance (NMR) in order to identify the molecular composition. 

Standard laboratory practices and procedures were followed. Eye protection and a functioning fume hood, glassware, magnetic and mechanical stirrers, chromatography columns and column materials, rotary evaporator, and vacuum pump were required. Chemicals for syntheses were either commercially available or synthesized by following the standard reported procedures. Compounds were routinely checked by solution nuclear magnetic resonance spectroscopy (NMR) and other appropriate spectroscopic and analytical methods. 

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