Parahydrogen discriminated PHIP at low magnetic fields

Parahydrogen induced polarization (PHIP) is a powerful hyperpolarization technique. However, as the signal created has an anti-phase characteristic, it is subject to signal cancellation when the experiment is carried out in inhomogeneous magnetic fields or in low fields that lack the necessary spectral resolution. The use of benchtop spectrometers and time domain (TD) analyzers has continuously grown in the last years and many applications are found in the food industry, for non-invasive compound detection or as a test bench for new contrast agents among others. In this type of NMR devices the combination of low and inhomogeneous magnetic fields renders the application of PHIP quite challenging. We have recently shown that the acquisition of J-spectra in high magnetic fields not only removes the anti-phase peak cancellation but also produces a separation of thermal from hyperpolarized signals, providing Parahydrogen Discriminated (PhD-PHIP) spectra. In this work we extend the use of PhD-PHIP to low and inhomogeneous fields. In this case the strong coupling found for the protons of the sample renders spin-echo spectra that have a great complexity, however, a central region in the spectrum with only hyperpolarized signal is clearly identified. This experimental approach is ideal for monitoring real time chemical reaction of pure PHIP signals.Fil: Prina, Ignacio. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Acosta, Rodolfo Héctor. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Optimized phases for the acquisition of J-spectra in coupled spin systems for thermally and PHIP polarized molecules

We demonstrate that the relative phases in the refocusing pulses of multipulse sequences can compensate for pulse errors and off-resonant effects, which are commonly encountered in J-spectroscopy when CPMG is used for acquisition. The use of supercycles has been considered many times in the past, but always from the view point of time-domain NMR, that is, in an effort to lengthen the decay of the magnetization. Here we use simple spin-coupled systems, in which the quantum evolution of the system can be simulated and contrasted to experimental results. In order to explore fine details, we resort to partial J-spectroscopy, that is, to the acquisition of J-spectra of a defined multiplet, which is acquired with a suitable digital filter. We unambiguously show that when finite radiofrequency pulses are considered, the off-resonance effects on nearby multiplets affects the dynamics of the spins within the spectral window under acquisition. Moreover, the most robust phase cycling scheme for our setup consists of a 4-pulse cycle, with phases yyyy‾ or xxxx‾ for an excitation pulse with phase x. We show simulated and experimental results in both thermally polarized and PHIP hyperpolarized systems.Fil: Bussandri Mattia, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Prina, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Acosta, Rodolfo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentin

Quasi-equilibrium states in thermotropic liquid crystals studied by multiple quantum NMR

Previous work showed that by means of the Jeener-Broekaert JB experiment, two quasiequilibrium states can be selectively prepared in the proton spin system of thermotropic nematic liquid crystals LCs in a strong magnetic field. The similarity of the experimental results obtained in a variety of LC in a broad Larmor frequency range, with crystal hydrates, supports the assumption that also in LC the two spin reservoirs, into which the Zeeman order is transferred, originate in the dipolar energy and that they are associated with a separation in energy scales: A constant of motion related to the stronger dipolar interactions S, and a second one W corresponding to the secular part of the weaker dipolar interactions with regard to the Zeeman and the strong dipolar part. We study the nature of these quasi-invariants in nematic 5CB 4-pentyl-4-biphenyl-carbonitrile and measure their relaxation times by encoding the multiple-quantum coherences of the states following the JB pulse pair on two orthogonal bases, Z and X. The experiments were also performed in powder adamantane at 301 K which is used as a reference compound having only one dipolar quasi-invariant. We show that the evolution of the quantum states during the buildup of the quasiequilibrium state in 5CB prepared under the S condition is similar to the case of powder adamantane and that their quasiequilibrium density operators have the same tensor structure. In contrast, the second constant of motion, whose explicit operator form is not known, involves a richer composition of multiple-quantum coherences of even order on the X basis, in consistency with the truncation inherent in its definition. We exploited the exclusive presence of coherences of 4,6,8, besides 0 and 2 under the W condition to measure the spin-lattice relaxation time TW accurately, so avoiding experimental difficulties that usually impair dipolar order relaxation measurement such as Zeeman contamination at high fields and also superposition of the different quasi-invariants. This procedure opens the possibility of measuring the spin-lattice relaxation of a quasi-invariant independent of the Zeeman and S reservoirs, so incorporating a new relaxation parameter useful for studying the complex molecular dynamics in mesophases. In fact, we report the first measurement of TW in a LC at high magnetic fields. Comparison of the obtained value with the one corresponding to a lower field 16 MHz points out that the relaxation of the W-order strongly depends on the intensity of the external magnetic field, similarly to the case of the S reservoir, indicating that the relaxation of the W-quasi-invariant is also governed by the cooperative molecular motions.Fil: Buljubasich Gentiletti, Lisandro. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monti, Gustavo Alberto. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Acosta, Rodolfo Héctor. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bonin, Claudio Julio. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: González, Cecilia Élida. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zamar, Ricardo César. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Singlet Spin Order Originating from Para-H2

Parahydrogen induced singlet spin order provides an excellent tool for many NMR/MRI applications in the natural sciences and medicine. The huge benefit of para-H2 for NMR experiments is two-fold: it represents a pure spin state that can be very efficiently used in hyperpolarization experiments, and its singlet spin order may make it long-lived because it is immune to many relaxation mechanisms. By the method of Parahydrogen Induced Polarization (PHIP), para-H2 can be introduced in certain molecules giving rise to hyperpolarized long-lived singlet spin states under favourable experimental conditions. In this chapter, the quantum mechanical properties of H2 are briefly introduced, the procedure for para-H2 enrichment is explained and the basic concept of para-H2 induced polarization (PHIP) is presented. The application of PHIP for the generation of hyperpolarized long-lived states in low and high magnetic fields is summarized. Because singlet spin states are NMR inactive, a special focus must be set on strategies for a controlled conversion of the singlet state into an NMR detectable triplet state. The advantages and disadvantages of several methods for accomplishing this goal are discussed.Fil: Münnemann, Kerstin. University of Kaiserslautern; AlemaniaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; ArgentinaFil: Franzoni, Maria Belen. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Resonancia Magnética Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

High-resolution hyperpolarized J-Spectra with Parahydrogen discrimination

Parahydrogen-induced polarization (PHIP) has become a powerful tool not only to overcome the low intrinsic sensitivity of nuclear magnetic resonance (NMR) but also as a probe for catalytic reactions, as a contrast agent in magnetic resonance imaging (MRI), or in analytic chemistry. In complex systems, the antiphase signals coming from parahydrogen in a PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) experiment can be partially canceled by the presence of large thermally polarized signals. In the present work, we present a simple method to separate the thermal and hyperpolrized contributions by taking advantage of their very different evolution during a modified CPMG sequence. The separation is obtained in combination with a property of the fast Fourier transform algorithm (FFT). The technique is experimentally demonstrated for a mixture of hyperpolarized 1-hexene and a large amount of CH2Cl2.Fil: Prina, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Acosta, Rodolfo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Diffusion measurements with continuous hydrogenation in PHIP

DOSY is a powerful spectroscopic NMR technique that resolves components in mixtures through the evaluation of different diffusion coefficients. The application of DOSY to dilute mixtures is hampered by the low signal to noise ratios (SNR), leading to long acquisition times. The use of PHIP may resolve this issue as long as reproducible signals are obtained in order to perform 2D experiments. Here we show that the use of hollow membranes and adequate gas flow produce constant polarization for a time-span that enables the acquisition of 2D experiments. A pressure gradient is evidenced by the presence of convection, which is accounted for by using a DPGSE sequence. The influence of J-coupling evolution during the sequence is studied both numerically and experimentally, to determine the optimum echo-time. The applicability of the method for samples with poor SNR is explored by setting the reaction rate to achieve a low intensity of polarized signals.Fil: Bussandri Mattia, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Acosta, Rodolfo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Combination of OPSY and PhD-PHIP results in enhanced sensitivity in PHIP

Despite the large degree of polarization in PHIP experiments compared to the Boltzmann factor, the presence of a large amount of non-reacted molecules with thermal polarization is an important obstacle when dealing with very diluted samples. The feasibility of enhancing both sensitivity and resolution in a single experiment by combining two well established pulse sequences, OPSY and PHD-PHIP is presented. OPSY is used as a block for filtering the signals originated from thermally polarized protons. PhD-PHIP, on the other hand, is used as an acquisition block, increasing the resolution and further improving the sensitivity by preventing signal canceling in the presence of magnetic field inhomogeneities. Experiments in a complex sample with very low hyperpolarization levels are presented showing the excellent performance of the method.Fil: Bussandri Mattia, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Acosta, Rodolfo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentin

Evolution of multiple quantum coherences with scaled dipolar Hamiltonian

In this article, we introduce a pulse sequence which allows the monitoring of multiple quantum coherences distribution of correlated spin states developed with scaled dipolar Hamiltonian. The pulse sequence is a modification of our previous Proportionally Refocused Loschmidt echo (PRL echo) with phase increment, in order to verify the accuracy of the weighted coherent quantum dynamics. The experiments were carried out with different scaling factors to analyze the evolution of the total magnetization, the time dependence of the multiple quantum coherence orders, and the development of correlated spins clusters. In all cases, a strong dependence between the evolution rate and the weighting factor is observed. Remarkably, all the curves appeared overlapped in a single trend when plotted against the self-time, a new time scale that includes the scaling factor into the evolution time. In other words, the spin system displayed always the same quantum evolution, slowed down as the scaling factor decreases, confirming the high performance of the new pulse sequence.Fil: Sánchez, Claudia Marina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Pastawski, Horacio Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Chattah, Ana Karina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentin

Discrimination of parahydrogen induced polarization signals with J-spectra acquisition in poorly hyperpolarized samples

The application of parahydrogen for the generation of hyperpolarization has increased continuously during the last years. When the chemical reaction that deposits the parahydrogen atoms into the target molecule is carried out following the PASADENA protocol an anti-phase signal is obtained, with a separation of the resonance lines of only a few Hz. Signal cancelation can be produced by line broadening due to magnetic field inhomogeneities or by the superposition with thermal signals. In this work we show that the acquisition of a J-spectrum has a double effect of enhancing spectral resolution and separating PHIP from thermal contributions even in systems where only a very small amount of hyperpolarization can be achieved.Fil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Prina, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Franzoni, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Acosta, Rodolfo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Discriminationof PHIP signals through their evolution in multipulse sequences

The antiphase character of the PHIP associated signals after a hydrogenation reaction is particularly sensitive to line broadening introduced by magnetic field inhomogeneities and interferences by the presence of resonance lines steaming from a large amount of thermally polarized spins. These obstacles impose a limitation in the detection of reaction products as well as in the experimental setups. A simple way to overcome these impediments consists of acquiring the signal with a train of refocusing pulses instead of a single r.f. pulse. We present here a number of examples where this multipulse acquisition, denominated PhD-PHIP, displays its potentiality in improving the information related to hyperpolarized spins performed in a sample, where the former parahydrogen nuclei are part of a complex J-coupling network.Fil: Bussandri Mattia, Santiago. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Franzoni, Maria Belen. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Acosta, Rodolfo Héctor. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin