Measurement of dilute Si-29 species in solution using a large volume coil and DEFT NMR

A large-sample-volume nuclear magnetic resonance (NMR) spectroscopy probehe ad has been developed for the detection and characterization of low concent rations of Si-29 species in aqueous solution. The approach described entail s the use of a large-diameter radio frequency solenoid coil that permits su bstantially larger sample volumes to be investigated at moderate magnetic f ield strengths, compared with conventional NMR probehead configurations. In addition, difficulties presented by long Si-29 T-1 relaxation times have b een circumvented by using the DEET NMR pulse sequence, which permits more r apid signal averaging, Through a combination of these hardware and methodol ogical improvements, high-resolution Si-29 NMR spectra have been obtained a t 4.2 T (29Si resonance frequency = 36.8 MHz) for an 800 mu M solution of 9 6% Si-29-enriched silicic acid, H4SiO4 (pH approximate to 8), With a signal -to-noise ratio of 16 and a line Width of 31 Hz after 3 h of total measurem ent time.