Carr-Purcell-Meiboom-Gill method

A. Methods. T measurements were made by the Carr-Purcell-Meiboom-Gill method tl4). spacings were agarose 200 sec soya fibres 300 isec raw and cooked/drained muscle 40 psec and cooked muscle 100 psec. 100 scans were accumulated in each case. 

The T and Ti values of water trapped in the silk fibroin gel were determined according to the usual inversion-recovery method and the Carr-Purcell-Meiboom-Gill method, respectively, with a JEOL FX-90Q NMR spectrometer at 90 MHz. Figure 35 shows the time dependence of the MR image of the swollen fibroin gel together with the distribution of the signal intensity of water across the sample (one-dimensional profile) after it was immersed in TEMPOL aqueous solution. 

Dinesh and Rogers [22,1] have also measured T and T2 for the proton in CHCl as a function of temperature (- 54°C to + 90 0. They employed an NMR Specialties multi-purpose NMR spectrometer. T2 was measured using the Carr-Purcell-Meiboom-Gill method and also by the adiabatic fast-passage method at room temperature. The sample of CHCl was carefully purified and degassed. The measured values around room temperature are... 

Deuterium NMR experiments were performed at 13.7 MHz on a JEOL FX 90Q spectrometer. The Ti measurements were performed using an inversion recovery sequence and the T2 values were estimated from the line widths. Because the resonances are relatively broad for the polymers in concentrated solutions, the Ta s measured were virtually the same as those measured from the Carr-Purcell-Meiboom-Gill (CPMG) method. In this case, measuring the line widths was much faster than measuring the T2 s by the CPMG method. Thus the T2 measurements were taken to be equivalent to the T2 s. 

The quadrupolar-echo experiment represents the most widely used experiment for the observation of quadrupolar nuclei.For half-integer nuelei, it may be tuned to observe only the central transition (1/2-1/2), which is perturbed by the quadrupolar interaction only to second order, thus allowing the observation of less dominant anisotropic interactions. A significant improvement in sensitivity can be obtained by ncorporating a spin-echo method such as the Carr-Purcell-Meiboom-Gill sequence into the detection period. " The powder line-shape splits into a manifold of sidebands, from which information on the homogeneous and inhomogeneous interactions can be extracted from the line-shape of the sidebands and their envelope, respectively. 

The transverse relaxation measurements are performed using a Hahn echo (see below) or Carr-Purcell-Meiboom-Gill (CPMG) pnlse sequences (18,19). The first method uses the pulse scheme 90J - t - 180j y - t - Hahn echo and measure the time evolution of the amplitude of the Hahn echo as afnnction of echo time 2r. 

CP and CPMG (Carr Purcell Meiboom Gill, Scheme 3b) measurements allow the method of analysis to be accelerated, but this is accompanied with a loss of any quantitative information. Silicon-29 NMR has also been used to study the level of fluorination of silica because the chemical shift is very sensitive to the number of fluorine atoms attached to silicon. " ... 

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