Complete elimination of the extracellular 23Na NMR signal in triple quantum filtered spectra of rat hearts in the presence of shift reagents.

A method is suggested whereby the shifted extracellular triple quantum filtered 23Na signal of an isolated organ is completely eliminated. The method is based on the long relaxation time of the triple quantum coherence and on its fast evolution rate. When the carrier frequency is set on top of the intracellular sodium signal and the time interval between the last two pulses to (12 delta nu)-1 (delta nu is the frequency difference between the intracellular and the extracellular signals), a complete elimination of the extracellular 23Na signal is achieved. The method is demonstrated for isolated rat hearts and the quantification of intracellular sodium using triple quantum filtered spectroscopy is discussed.