REfocused INADEQUATE spin-Echo

Figure 12 Pulse sequence and corresponding coherence transfer pathway diagram for (A) the z-filtered spin-echo (B) the refocused INADEQUATE and (C) the refocused INADEQUATE spin-echo (REINE) experiments.Thin and thick rectangles, respectively, represent n/1 and n pulses. Taken from Ref. [65].

Very recently, Cadars et al. have presented a new modification of refocused INADEQUATE pulse sequence with the acronym REINE (REfocused INADEQUATE spin-Echo).64 As shown in Figure 12, the REINE joins two known approaches. The additional spin-echo period in the REINE experiment allows the detection of the /-modulation for each 2D peak. 

Very recently, Brown and co-workers65 published a concise paper in which they presented short review of the possibilities and limitations of the refocused INADEQUATE and refocused INADEQUATE spin-echo (REINE) NMR spectroscopy. The authors discussed how these experiments can be used for obtaining various structural parameters, for example identification phosphate units, phosphate chain length, 2/p p couplings and correlation with chemical shift. It is worthy of note that the approach presented there can be applied not for phosphate glasses alone. 

The operation of the proton-enhanced sequences is best understood by reference to the original INEPT-INADEQUATE sequence shown in simplified form in Fig. 5.80 in which the individual component parts have been identified and may be followed in a stepwise manner. Thus, initial transfer from proton to carbon is via the INEPT sequence introduced in Chapter 4 followed by the generation of DQC as for the INADEQUATE above. This again evolves to encode c after which gradient selection begins. The DQ then returns to single quantum, and the C- C-coupling is refocused by the spin-echo. The final step is INEPT in reverse to transfer from carbon back onto proton, followed by... 

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