Water attenuation by T2 relaxation

WATR, WEFT and Water-PRESS. If the transverse relaxation of the water is faster than the spins of interest, suppression can be achieved using the CPMG-based WATR (water attenuation by T2 relaxation) method. ° The T2 relaxation time of the water can be selectively decreased through the... 

T-90°-data acquisition [9] in which the time interval, x, is chosen such that the water resonance, which is expected to have the longest T, in the sample, has zero magnetization after the 90° pulse [113, 114], The CPMG spin-echo pulse sequence 90°-(t-180°-t) n-data acquisition (n = number of repetitions), has been used with the pulse interval, r, adjusted to attenuate the water signal, for example, from erythrocyte and protein suspensions [113], The technique is improved by the addition of ionic species such as ammonium chloride which increases the chemical exchange of the water protons and thus shortens T2 relative to the compounds of interest. This method is known as WATR (Water Attenuation by T2 Relaxation) [114]. Solvent suppression can also be achieved by selective excitation of the spectrum with special pulses such that the water resonance occurs at a point of null excitation [115-119]. However, distortion of peaks near the null point may occur. 

The investigation of the ester hydrolysis reaction can take advantage of the suppression of the water signal by means of the WATR technique (water attenuation by T2 relaxation). Using this method, signals in the region of J = 4-5 ppm can easily be observed. In this manner, the kinetics of hydrolysis of neostigmine bromide in weak acid aqueous solution... 

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