APPLICATION OF THE WATR TECHNIQUE FOR WATER SUPPRESSION IN H-1-NMR SPECTROSCOPY IN DETERMINATION OF THE KINETICS OF HYDROLYSIS OF NEOSTIGMINE BROMIDE IN AQUEOUS-SOLUTION

Both ammonium chloride and guanidinium chloride were used to secure water suppression in H-1 NMR spectra using the 'Water Attenuation by T2 Relaxation' (WATR) technique. The effect of phosphate buffer in the suppression was investigated over a range of pH values at 80 MHz. The spin-spin relaxation time of water protons at 80 MHz was found to reach a minimum at pH 7.3 in the presence of 0.1 M phosphate buffer and 1 m guanidinium chloride; these conditions were therefore chosen for subsequent use of the WATR technique in a study of the kinetics of hydrolysis of neostigmine bromide. The method was found to be very convenient for studies of the hydrolysis of this representative amide.