PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 10783284

Combining PGSE NMR with homonuclear dipolar decoupling.

S V Dvinskikh·I Furó
View original source ↗Export metadata ↓

Abstract

A new robust approach for combining multiple-pulse homonuclear decoupling and PGSE NMR is introduced for accurately measuring molecular diffusion coefficients in systems with nonvanishing static homonuclear dipolar couplings. Homonuclear decoupling suppresses dipolar dephasing during the gradient pulses but its efficiency and scaling factor for the effective gradient vary across the sample because of the large variation of the frequency offset caused by the gradient. The resulting artifacts are reduced by introducing a slice selection scheme. The method is demonstrated by (19)F PGSE NMR experiments in a lyotropic liquid crystal.

Explore related subjects

CalibrationCesiumCrystallizationDiffusionFluorine RadioisotopesMagnetic Resonance SpectroscopyWaterJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

S V Dvinskikh, I Furó. 2000. Combining PGSE NMR with homonuclear dipolar decoupling.. https://doi.org/10.1006/jmre.2000.2027

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Fermentation process tracking through enhanced spectral calibration modeling.

The FDA process analytical technology (PAT) initiative will materialize in a significant increase in the number of installations of spectroscopic instrumentation. However, to attain the greatest benefit from the data generated, there is a need for calibration procedures that extract the maximum information content. For example, in fermentation processes, the interpretation of the resulting spectra is challenging as a consequence of the large number of wavelengths recorded, the underlying correlation structure that is evident between the wavelengths and the impact of the measurement environment. Approaches to the development of calibration models have been based on the application of partial least squares (PLS) either to the full spectral signature or to a subset of wavelengths. This paper presents a new approach to calibration modeling that combines a wavelength selection procedure, spectral window selection (SWS), where windows of wavelengths are automatically selected which are subsequently used as the basis of the calibration model. However, due to the non-uniqueness of the windows selected when the algorithm is executed repeatedly, multiple models are constructed and these are then combined using stacking thereby increasing the robustness of the final calibration model. The methodology is applied to data generated during the monitoring of broth concentrations in an industrial fermentation process from on-line near-infrared (NIR) and mid-infrared (MIR) spectrometers. It is shown that the proposed calibration modeling procedure outperforms traditional calibration procedures, as well as enabling the identification of the critical regions of the spectra with regard to the fermentation process.

Calibration↗
PubMed2007

Particle sizing with a fast polar nephelometer.

We reported previously the design of a polar nephelometer that uses a rotational confocal imaging setup to enable fast scanning of the scattering phase function within a field of view of 55 degrees . The full dynamic range of the detection system can be used by increasing the signal-to-noise ratio by means of averaging successive scans. The calibration of the angular response of the instrument is achieved by obtaining the transfer function of the optical detection system using Rayleigh scatterers. Accurate particle sizing of individual polystyrene spheres (ranging from 1.5 to 9 micro m in diameter) in aqueous suspension is achieved by maximizing a correlation coefficient between precalculated tables of Mie phase functions and data obtained from the polar nephelometer. Good correlation is achieved between experimental and theoretical data, proving the functioning of the instrument as a fast and convenient particle sizer.

Calibration↗
PubMed2007

Online standard additions calibration of transient signals for inductively coupled plasma mass spectrometry.

An online standard additions calibration method for transient signals in ICPMS is demonstrated in which a small volume of standard is injected as a spike into the sample/carrier stream, overlaying the analyte peak. This technique provides the advantages of conventional standard additions but requires only a single sample run. The method corrects for matrix effects and is suitable for transient signals in which the severity of the matrix effect changes over the analyte peak. The method uses a peak-fitting program to determine the area of the underlying peak and is shown to be effective for the determination of trace metal concentrations in both a high ionic strength matrix and in a biological matrix (urine). Eight analytes with concentrations in the range of 0.82-233.2 mug L-1 in urine were simultaneously determined using a standard spiking solution of 75 mug L-1 injected through a 100-muL loop. The measured concentrations for analytes free of spectral interferences agreed with the certified values, and the precision achieved was comparable to that achieved by the certifying agency. Using a conventional cross-flow nebulizer and Scott-type spray chamber, the accuracy obtained for online standard additions calibration was within 2%, and the precision was within 5%.

Calibration↗