Improved applicability of DOSY experiments by high resolution probes combined with gradient amplifiers of diffusion units

Abstract

Short relaxation times and small diffusion coefficients often impede reliable diffusion experiments due to insufficient signal to noise ratios, especially in low temperature studies, where in the case of small diffusion coefficients in combination with very short T(2) times and substantial convection, double-stimulated-echo experiments are required as last resort of convection-compensating DOSY pulse sequences. Therefore, the combination of a strong gradient amplifier of a diffusion unit with Z-gradient high resolution probes is tested for low temperature applications to combine the advantages of high (1)H resolution, flexible temperature, and multinuclear applications with short gradient durations and diffusion delay. The experimental spectra on phosphoramidite ligands and phosphoramidite-copper complexes show that signal to noise improvements up to 176% were achieved despite longer eddy current delays and increased noise levels. Calculational estimations of the enhancement factors predict special benefits for systems with short transversal relaxation times and small diffusion coefficients and promise even higher enhancement factors for noise level optimized combinations. In addition, an easy way is presented to find fast and effectively relaxation optimized DOSY parameters for the convection-compensated double-stimulated-echo pulse sequence of Jerschow and Müller.

Diffusion-Tensor Imaging Assessment of White Matter Maturation in Childhood and Adolescence

“…Many studies now use a larger number of diffusion-encoding directions, which provide a more representative measurement of the diffusion tensor. Nonetheless, a recent study indicates that the number of diffusion gradients does not substantially affect the signal-to-noise ratio of FA and ADC maps [32]. Finally, evaluation of the individual principle eigenvalues is seen by some investigators as a more definitive method of assessing white matter integrity [33, 34].…”

Applications of NMR diffusion methods with emphasis on ion pairing in inorganic chemistry: a mini‐review

“…Using this method, it was possible to detect the presence of intermediate oligomeric species of diphenyl alanine in solution during the process of its self‐assembly to form nanotubular structures. In yet another report, DOSY experiments on phosphoramidite ligands and phosphoramidite copper complexes, signal to noise improvements up to 176% were achieved …”

“…Figures and show several of these many sequences. A series of relatively recent publications deal with suggestions for improving the various aspects of the measurement . These include problems concerned with steady state effects in a two‐pulse diffusion‐weighted sequence, convection, band‐selective radio frequency pulses, J‐coupling peak distortion, short diffusion times, 3D DOSY, TOCSY, data processing for DOSY and high temperature measurements .…”

“…A series of relatively recent publications deal with suggestions for improving the various aspects of the measurement. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] These include problems concerned with steady state effects in a two-pulse diffusion-weighted sequence, [14] convection, [15] band-selective radio frequency pulses, [16] J-coupling peak distortion, [20] short diffusion times, [21] 3D DOSY, [24,25] TOCSY, [26] data processing for DOSY [22] and high temperature measurements. [18] A recent publication, involving '2D FAST DOSY' [27] offers the use of a single 2D spectrum to measure diffusion rates.…”

“…In yet another report, DOSY experiments on phosphoramidite ligands and phosphoramidite copper complexes, signal to noise improvements up to 176% were achieved. [28]…”