3 mm Micro-dual probe

Aside from the obvious improvement in the s/n ratio, which arises in part from concentrating the sample from 145 to 40 pL as well as from having all of the sample in the rf coil rather than 70%, the ketone carbonyl resonance at 219.5 ppm was observed with reasonable signal intensity whereas its presence was questionable at best in the 3 mm micro-dual probe 13C spectrum shown in the top panel. The s/n ratios of the overnight acquisitions were 5.5 1 for the 3 mm micro-dual probe vs. 11 1 for the Nano-probe . There is no obvious reason why the carbonyl resonance was not observed in the 3 mm micro-dual 13C spectrum, as the relaxation delay between acquisitions was set identically in the two experiments. These data also suggest that on a per-transient basis, that the performance of the Nanoprobe is perhaps somewhat lower than that of the 3 mm micro-dual probe. This inference is based on the nearly 4-fold concentration difference between the two probe formats. Assuming probe efficiencies were identical, an s/n ratio approaching 22 1 should have been observed for the Nano-probe based on the concentration increase. 

Later in 1996 the first example of a dimeric indoloquinoline alkaloid, crypt-omisrine (22), was isolated and its structure elucidated.73 Inverse-detected 2D-NMR spectra were recorded using a 3 mm micro-inverse probe 13C chemical shift data were recorded for the sample using a 3 mm micro-dual probe. In addition to the mass spectral data, a 0.9% nuclear overhauser effect (NOE) observed between the HI and H9 protons was used to confirm the structure. 

Musser and colleagues utilized 3 mm micro-probe technology in a study reporting the identification of a new series of fumonisins containing 3-hydroxypyridine moieties (24A-C).77 A 400 MHz 3 mm micro-dual probe was used to both record 13C spectra as well as for the acquisition of HMQC and HMBC data used in the characterization of these fungal secondary metabolites. 

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