Incredible natural abundance double sensitivity

The incredible natural abundance double quantum transfer experiment (INADEQUATE) was proposed by Ray Freeman in 1980.1 2 The acronym of this remarkable technique sat high among the many NMR acronyms since, at the time of its birth, it accurately described all its attributes. INADEQUATE was seen as an incredible experiment with vast potential its widespread applications are dwarfed only by its inadequate sensitivity. Depending on the equipment available, an ovemight-to-weekend INADEQUATE experiment on a medium-sized molecule would typically require hundreds of milligrams of sample. Only recently have such unfavourable requirements been addressed with advent of cryogenically cooled probes. Now, INADEQUATE experiments using samples of 5-10 mg have become realistic propositions. 

INADEQUATE (Incredible Natural Abundance Double Quantum Transfer Experiment). On one axis one has the C-NMR spectrum while on the other axis the double quantum frequencies are present (Englert 1985). A direct carbon-carbon coupling is indicated by a pair of doublets at a certain double quantum frequency. In this experiment, in fact the C satellites of C signals are observed. It must be clear that this method has a low sensitivity, because two adjacent C nuclei are required. 

The least sensitive of all experiments is the incredible natural abundance double quantum transfer experiment (INADQUATE), as it involves detection of correlations between pairs. These spins occur together in only... 

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