Parahydrogen discriminated signals used as a detection block with improvedresolution

ACOSTA, R.H.; BULJUBASICH, L.; BUSSANDRI, S.

Congreso; PERM2020; 2020

The signal enhancement in PHIP experiments if often reduced by a number of factors, being the most common ones line broadening due to B0 inhomogeneities and spectral superposition with signals originated from thermally polarized molecules. We have proposed a solution to these topics by introducing the idea of acquiring PHIP signals during a train of refocusing pulses with specic phases, namely Parahydrogen Discriminated PHIP (PhD-PHIP) [1,2]. The different evolution of thermal and PHIP induced signals during this CPMG-like pulse sequence results in a large spectral separation upon Fast Fourier Transformation, enabling the clear identification of PHIP signals. In this way, partial J-spectra with information only concerning hyperpolarized molecules is obtained with improved resolution and sensitivity. Furthermore, the method can be easily implemented at low field equipment with very low magnetic field homogeneity for monitoring chemical reactions [3]. In the case of highly diluted samples, however, sensitivity still may pose a problem. In PhD-PHIP thermal signals are not removed but rather shifted to an entirely different part of the J-spectrum, still imposing a limitation in the settings of the receiver gain. This issue was tackled by the combination of OPSY (Only Parahydrogen SpectroscopY) as an encoding block and PhD-PHIP as a detection block, resuting in clear spectra as showin in the above figure [4]. In this presentation we will focus on the working principles of PhD-PHIP and explore the potential of combinig different pulse sequences for signal encoding. In particular we show results using a set of hollow Teflon membranes for parahydrogen dissolution on a target sample, which renders highly reproducible signals that enable the acquisition of 2D data sets. We will show a successful implementation of DOSY+PhD-PHIP where a double encoded pulsed field gradient was used to account for convexion. [1] L. Buljubasich, I. Prina, M.B. Franzoni, K. Münnemann, H.W. Spiess, and R.H. Acosta. High resolution para-hydrogen induced polarization in inhomogeneous magnetic fields. Journal of Magnetic Resonance, 230:155-159, 2013. [2] I. Prina, L. Buljubasich, and R. H. Acosta. High-Resolution Hyperpolarized J-Spectra with Parahydrogen Discrimination. J. Phys. Chem. Lett., 4(22):3924-3928, 2013. [3] I. Prina, L. Buljubasich, and R.H. Acosta. Parahydrogen discriminated PHIP at low magnetic fields. Journal of Magnetic Resonance, 251:1-7, 2015. [4] S. Bussandri, L. Buljubasich, and R.H. Acosta. Combination of OPSY and PhD-PHIP results in enhanced sensitivity in PHIP. Journal of Magnetic Resonance, 299:28-32, 2019.