Investigating the sensitivity limits of 13C-detected 1H-13C chemical shift correlation sequences with modern microprobe and microtube technology
Por:
Reynolds W.F., Yu M., Enriquez R.G.
Publicada:
1 ene 1997
Resumen:
The sensitivity limits for 13C-detected 13C-1H shift correlation sequences were evaluated using a microprobe in combination with 3 mm microtubes fitted with susceptibility plugs which allow for further restriction of the sample volume. For an absolute value BIRD-decoupled HETCOR spectrum acquired in 4-5 h, the sensitivity limit for compounds with non-equivalent CH2 groups in ca. 3 ?mol of sample, with significantly lower limits for compounds with only CH and/or CH3 groups. For an absolute value n-bond spectrum acquired with the FLOCK sequence in 16 h, a similar amount of sample is barely adequate to observe cross peaks from CH3 singlets while a spectrum showing a large number of n-bond peaks to CH, CH2 and CH3 protons requires about 15 ?mol of sample. Further sensitivity gains could be realized by using phase-sensitive versions of the two sequences. While these experiments still fall considerably short of the corresponding limits for HMQC and HMBC using a similar 1H-optimized microprobe, the 13C-detected experiments can give significantly better 13C resolution, hence they may still be advantageous for organic structure elucidation in cases where 13C resolution is critical. © 1997 by John Wiley & Sons, Ltd.
Filiaciones:
Reynolds W.F.:
Department of Chemistry, University of Toronto, Toronto, Ont. M5S 3H6, Canada
Yu M.:
Department of Chemistry, University of Toronto, Toronto, Ont. M5S 3H6, Canada
Enriquez R.G.:
Instituto de Quimica, Univ. Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacan, D.F. 04510, Mexico
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