On resonance phase alternated CWFP sequences for rapid and simultaneous measurement of relaxation times

Monaretto, Tatiana; Andrade, Fabiana Diuk; Moraes, Tiago Bueno; Souza, Ademária Aparecida de; deAzevedo, Eduardo R.; Colnago, Luiz Alberto

doi:10.1016/j.jmr.2015.08.013

Cited by 19 publications

(22 citation statements)

References 21 publications

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“…Figures show the influence of 1:1 [Cu 2+ ‐Sorb] complex on the T 1 (■) and T 2 (○) relaxation times of the aqueous solution in function of pH. The relaxation times were measured simultaneously, in a single experiment, using the CP‐CWFP x‐x pulse sequence . Conversely to older CWFP and CP‐CWFP pulse sequences, the 180° phase alternation in CP‐CWFP x‐x yields signals with high dynamic range, independent of T 1 /T 2 ratio.…”

Section: Resultsmentioning

confidence: 99%

“…The NMR relaxometric experiments were performed using a 0.47 T spectrometer (19.90 MHz for 1 H), minispec, Bruker, model mq20, at 25.0 ± 0.1°C. The values for longitudinal (T 1 ) and transverse (T 2 ) relaxation times were simultaneously obtained applying the CP‐CWFP x‐x pulse sequence, using π/2 pulses with a duration of 2.34 μs, recycling time of 9.0 s, 4 scans, and 28,000 echoes. The relaxation times were calculated using monoexponential fittings using Origin, version 9.0.…”

Section: Methodsmentioning

confidence: 99%

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Magnetic resonance studies of copper (II) sorbitol complex, in solution, reveal a supramolecular structure compatible to the crystal structure

Kock

Higuera-Padilla

Vigatto

et al. 2019

Magnetic Reson in Chemistry

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Although the Cu2+‐sorbitol complex [Cu2+‐Sorb] structure in crystalline state has been determined by X rays, it is not known in solution, where most studies of this complex are performed. Therefore, the goal of this work was to obtain information about the structure of this complex in aqueous solution using nuclear magnetic resonance and electron paramagnetic resonance spectroscopies. The magnetic resonance results indicate that the complex is formed at approximately pH 12. In this pH the sorbitol 1H relaxation times were so short (broad line) that was not possible to use standard nuclear magnetic resonance parameters (nuclear Overhauser effect and spin–spin coupling constants values) to solve the three‐dimensional structure. However, valuable structural information about the complex in solution was obtained. The relaxation results indicate that the Cu2+ ions are buried in the structure and not accessible to solvent; the 1H and 13C spectra shows strong paramagnetic shift effect indicating short distance between these nuclei and Cu2+ in the structure. No electron paramagnetic resonance signal was observed in pH 12 indicating strong Cu2+‐ Cu2+ dipolar interaction, compatible to Cu2+‐Cu2+ distances measured in crystal, from 1.148 to 1.393 Angstroms. The complex self‐diffusion coefficient (D) of 1.58 × 10−10 m2/s value, determined by Diffusion‐Ordered Spectroscopy, is compatible to a molecular weight of 3–6 KDa. Therefore, these results corroborate that the [Cu2+‐Sorb] complex is assembled in solution, at pH 12, with several structural parameters compatible to the toroidal hexadecacuprate supramolecular structure determined in solid state.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Magnetic resonance studies of copper (II) sorbitol complex, in solution, reveal a supramolecular structure compatible to the crystal structure

Kock

Higuera-Padilla

Vigatto

et al. 2019

Magnetic Reson in Chemistry

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“…These nulls and maximums of amplitude occur due to the destructive or constructive interference between the FID and echo components in the SSFP sequences [12]. These complex interferences between FID and echo signals depend on the time interval between pulses T p , precession angle Φ, frequency offset Ω, flip angle θ, and phase alternation [23,24].…”

Section: Introductionmentioning

confidence: 99%

“…All the proprieties of CWFP methods make them an important tool for industrial protocols, as well as in quantitative analysis where CWFP can enhance the SNR compared with conventional CPMG or FID protocols [14][15][16][17][18][19][20][21][22].In this review, we outline SSFP/CWFP theory and their applications in low field TD-NMR to enhance SNR, in quantitative analyses, in flow analyses, in thermal diffusivity measurements, for fast simultaneous measurements of T 1 and T 2, , and in the fast T 1 method. CWFP methods have been applied in many conventional TD-NMR spectrometers, such as the Minispec mq20, Bruker (0.47 T) [23], Maran Ultra (0.54 T) [24], SLK-100, SpinLock (0.28 T) [25,26], Tecmag spectrometer [27], and Oxford instrumentations [28,29]. The complete ExpSpel code used to implement the CWFP pulse sequence in the Minisepc mq20 spectrometer, Bruker (NF electronics) is available in the Supplementary Materials.…”

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confidence: 99%

Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR

2019

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This review discusses the theory and applications of the Continuous Wave Free Precession (CWFP) sequence in low-field, time-domain nuclear magnetic resonance (TD-NMR). CWFP is a special case of the Steady State Free Precession (SSFP) regime that is obtained when a train of radiofrequency pulses, separated by a time interval T p shorter than the effective transverse relaxation time (T 2 *), is applied to a sample. Unlike regular pulsed experiments, in the CWFP regime, the amplitude is not dependent on T 1 . Therefore, T p should be as short as possible (limited by hardware). For T p < 0.5 ms, thousands of scans can be performed per second, and the signal to noise ratio can be enhanced by more than one order of magnitude. The amplitude of the CWFP signal is dependent on T 1 /T 2 ; therefore, it can be used in quantitative analyses for samples with a similar relaxation ratio. The time constant to reach the CWFP regime (T*) is also dependent on relaxation times and flip angle (θ). Therefore, T* has been used as a single shot experiment to measure T 1 using a low flip angle (5 • ) or T 2 , using θ = 180 • . For measuring T 1 and T 2 simultaneously in a single experiment, it is necessary to use θ = 90 • , the values of T* and M 0 , and the magnitude of CWFP signal |M ss |. Therefore, CWFP is an important sequence for TD-NMR, being an alternative to the Carr-Purcell-Meiboom-Gill sequence, which depends only on T 2 . The use of CWFP for the improvement of the signal to noise ratio in quantitative and qualitative analyses and in relaxation measurements are presented and discussed.to suppress these anomalies using a small variation of T p that cancels the echo component. In the same year, Schwenk [4] proposed the Quadriga Fourier Transform (QFT) to suppress these anomalies. The QFT method was based on a small variation in frequency offset. Although these procedures minimize these anomalies, SSFP sequences were not routinely used in high resolution NMR.We revised these methods and suggested some modifications to increase the applications of SSFP in high-resolution NMR using the Traff apodization function [5] to minimize the truncation problem, or processing the SSFP time domain signal with a parametric method based on Krylov Basis Diagonalization Method (KBDM) [6]. KBDM solves the truncation and phase anomalies but not the amplitude problem. Therefore, SSFP sequences cannot be used to efficiently enhance signal to noise ratio (SNR) in high-resolution NMR. SSFP sequences have been successfully used in magnetic resonance imaging [7,8] and in low-field, time-domain NMR [9][10][11]. The use of a SSFP sequence in low field time domain (TD-NMR) started in year 2000 [12,13]. The applications of SSFP sequences in TD-NMR can be performed under the drastic condition where T p < 1 ms. Under this condition, a truly continuous wave free precession (CWFP) regime is obtained [13]. Normally, CWFP sequences use T p < 0.5 ms, as T p has to be shorter than T 2 *, which is in the order of 1 ms in most TD-NMR spectrometers.In the CWFP regime, F...

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“…Therefore, it is possible to obtain T 1 and T 2 just by measuring the intensity of the signal after the first pulse, proportional to M 0 , M CWFP , and T *. Two other variations of CWFP sequence were developed to enhance dynamic range of T * measurement and to perform the experiments on resonance . Although those CWFP sequences have been useful in several applications to measure T 1 and T 2 in rapid and single‐shot experiments, they have been limited to spectrometers with short dead times (around 10 μs) to allow an accurate estimation of M 0 .…”

Section: Introductionmentioning

confidence: 99%

Enhancing signal‐to‐noise ratio and resolution in low‐field NMR relaxation measurements using post‐acquisition digital filters

Monaretto

Souza²,

Moraes

et al. 2018

Magnetic Reson in Chemistry

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The traditional way to enhance signal‐to‐noise ratio (SNR) of nuclear magnetic resonance (NMR) signals is to increase the number of scans. However, this procedure increases the measuring time that can be prohibitive for some applications. Therefore, we have tested the use of several post‐acquisition digital filters to enhance SNR up to one order of magnitude in time domain NMR (TD‐NMR) relaxation measurements. The procedures were studied using continuous wave free precession (CWFP‐T1) signals, acquired with very low flip angles that contain six times more noise than the Carr–Purcell–Meiboom–Gill (CPMG) signal of the same sample and experimental time. Linear (LI) and logarithmic (LO) data compression, low‐pass infinity impulse response (LP), Savitzky–Golay (SG), and wavelet transform (WA) post‐acquisition filters enhanced the SNR of the CWFP‐T1 signals by at least six times. The best filters were LO, SG, and WA that have high enhancement in SNR without significant distortions in the ILT relaxation distribution data. Therefore, it was demonstrated that these post‐acquisition digital filters could be a useful way to denoise CWFP‐T1, as well as CPMG noisy signals, and consequently reducing the experimental time. It was also demonstrated that filtered CWFP‐T1 method has the potential to be a rapid and nondestructive method to measure fat content in beef and certainly in other meat samples.

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On resonance phase alternated CWFP sequences for rapid and simultaneous measurement of relaxation times

Cited by 19 publications

References 21 publications

Magnetic resonance studies of copper (II) sorbitol complex, in solution, reveal a supramolecular structure compatible to the crystal structure

Magnetic resonance studies of copper (II) sorbitol complex, in solution, reveal a supramolecular structure compatible to the crystal structure

Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR

Enhancing signal‐to‐noise ratio and resolution in low‐field NMR relaxation measurements using post‐acquisition digital filters

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