High resolution spectra in PHIP

R.H. ACOSTA; I. PRINA; L. BULJUBASICH

Gas Phase NMR

Royal Society of Chemistry

Año: 2016; p. 306 - 337

This chapter reviews the recent development of an NMR method to obtain information of site selective hyperpolarized samples by Parahydrogen Induced Polarization (PHIP) were the chemical reaction is carried out at high magnetic fields (PASADENA). The method relies on the acquisition of J-spectra in PHIP, which is different than J-spectra for thermally polarized species due to the different evolution in the time domain during the application of a Carr-Purcell-Meiboom-Gill (CPMG) sequence. Signals originated due to PHIP and thermal polarizations are centred in spectral positions that are shifted by half of the spectral width. This effect gives rise to two useful results. On one hand, the antiphase character of PASADENA spectra implies a partial peak cancellation, as J-couplings introduce a splitting in the signal of a few Hz. The acquisition of J-spectra renders linewidth typically of 0.1 Hz, thus avoiding signal cancellation. A second aspect to be considered in PHIP is the suppression of antiphase signals due to the overlap with ones steaming from thermal polarization with the same frequency. In this case, the frequency discrimination of the method enables the detection of hydrogenation even for very low reaction rates. Thus, the method is referred to as Parahydrogen Discriminated PHIP (PhD-PHIP). Application of PhD-PHIP for the study of hyperpolarized gases is discussed and simulations of the performance of the method are presented.