Multiple Coils Connected in Parallel

The resonance frequencies of the peaks in the four samples will shift by different amounts when the gradient is applied. Suppose that sample A is placed in coil 1, and that it has a single NMR resonance. The resonant frequency, 00a, is then given by the following  

One method of reducing the effects of the line-broadening due to the z-gradient present during data acquisition is to use reference deconvolution  

These methods work well for spectra in which there is no significant spectral overlap between compounds, or for situations where the samples to be analysed are chemically quite similar. For example, parallel process monitoring could be accomplished by using such an approach. In cases where spectra contain many resonances that overlap, it is much more difficult to assign resonances based on frequency shifts. Two other approaches have been used in this case [15,16]. One 

Selective excitation is an efficient method of data collection for samples in which the value of the relaxation time (TRc j) is less than three times the T value of the sample. The smallest possible value of 77 eff is given by n times the data acquisition time for each sample, where n is the number of coils. In cases where very high spectral resolution is required, a large number of coils are used, and/or where the samples have short T values, this method may be of limited use. The use of multiple receivers interfaced with a number of arrays, each containing a smaller number of coils, can potentially overcome this limitation. Alternatively, a one-dimensional CSI method can be used, with the proviso of losses in S/N or potentially longer acquisition times, as mentioned earlier. 

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