Broadband multinuclear probe

Larger format probes, e.g., 12,18 and 22 mm facilitate the study of rare nuclei such as 15N and 170. X-nucleus or broadband multinuclear... 

An architecture which offers more variability is based essentially on a multinuclear probe head whose H coil is triply tuned to deliver the additional " Y frequency and offers the possibility to perform triple-resonance experiments with a fixed nucleus Y, but a choice of "X. The selection of the fixed channel depends on the intended usage the most common options are and C which offer widespread applicability in organometallic and coordination chemistry. For a good performance it is mandatory that RF interferences between the different channels are eliminated by appropriate filtering. Even if this arrangement is still less flexible than a probe head in which both "X and ""Y are variable, it appears preferable because the presence of two tuneable broadband coils would probably lower sensitivity, and the handling would be rather difficult because of increased RF interference problems. 

Lineshape and resolution tests on other nuclei follow a similar procedure to that above. Not all nuclei available with a given probe need be tested and typically only tests for inner and outer coil observations on multinuclear probes are required. This means the second test will often involve carbon-13 for which two samples are in widespread use the ASTM (American Society for Testing and Materials) test sample (40% p-dioxane in deuterobenzene also used for the sensitivity test) or 80% benzene in deuteroacetone. In either case on-resonance continuous-wave (CW) decoupling of protons should be used as this provides improved results for a single resonance relative to broadband decoupling. Rather long (30-40 s) acquisition times will be required for a well shimmed system. 

All modern high-field NMR spectrometers come equipped with broadband tunable probes that can be used for multinuclear NMR spectroscopy. The phosphorus nucleus is particularly easy to detect, being spin = 1 and 100% abundant. Figure 11.10 is a P-NMR spectrum of a... 

P and Sn NMR spectra were recorded on a Varian XL 300 FT-NMR spectrometer equipped with a multinuclear broadband probe and operated at 121.42 and 111.86 MHz, respectively. P NMR spectra were recorded by setting triphenyl phosphate (in CDCI3) at (P) = — 18 ppm relative to 85% H3PO4 see J. Emsiey and D. Hall, The Chemistry of Phosphorus, Wiley, New York, 1976, p. 82. Upheld shifts are negative. 

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