PNNL

Abstract

The increase in the sensitivity of the phase-corrected magic angle turning (PHORMAT) experiment at ultra slow spinning rates by means of multiple-echo data acquisition (ME-PHORMAT) is evaluated. This is achieved by replacing the acquisition dimension in the original experiment with a train of equally spaced p pulses. It is shown that the echoes following the odd and even p pulses in the CPMG train must be processed differently in order to avoid spectral distortions. The method is illustrated for 13C CP-ME-PHORMAT on solid 1,2,3-trimethoxybenzene and for 1H ME-PHORMAT on excised rat liver tissue, both at a sample-spinning rate of 1.3 Hz. Sensitivity enhancements of a factor 4 for the solid and 2.3 for the liver were obtained. Finally, it is shown that with ME-PHORMAT one of the two RF pulse sequences, in standard PHORMAT used to obtain a pure absorption mode 2D spectrum, can be eliminated, thus reducing the usually long measuring time by a factor 2.