DIRECT ANALYSIS OF CRUDE REACTION MIXTURE OF A PHOTOCATALYTIC CH-ARYLATION REACTION VIA MOLECULAR ROTATIONAL RESONANCE SPECTROSCOPY

A number of recent review articles have summarized the application of Molecular Rotational Resonance (MRR) spectroscopy to the area of molecular structure determinations and described how these applications have applied to chemistry. This article will briefly review this established area of MRR spectroscopy and describe two developments that offer the promise of expanding the applicability of MRR spectroscopy. The first development was the observation that some large molecules (by MRR standards) give a series of relatively intense, equally spaced bands that can be quickly recorded and assigned. The other development has been in the theory, procedures, and instrumentation required for accurate intensity measurements. These two developments, examples of each, and the implication of each for use by chemists, as well as molecular structure determinations, will be discussed. Spectrometers that are being used for studies in this established area and the two newer areas will be described in the Appendix.

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Systematic comparison of post-column isotope dilution using LC-CO-IRMS with qNMR for amino acid purity determination

Analytical and Bioanalytical Chemistry ◽

10.1007/s00216-019-02116-2 ◽

2019 ◽

Vol 411 (27) ◽

pp. 7207-7220

Author(s):

Philip J. H. Dunn ◽

Dmitry Malinovsky ◽

Eli Achtar ◽

Cailean Clarkson ◽

Heidi Goenaga-Infante

Keyword(s):

Measurement Uncertainty ◽

Isotope Dilution ◽

International System ◽

Direct Analysis ◽

Uncertainty Budget ◽

Chemical Oxidation ◽

Resonance Spectroscopy ◽

Purity Determination ◽

System Of Units

Abstract Determination of the purity of a substance traceable to the International System of Units (SI) is important for the production of reference materials affording traceability in quantitative measurements. Post-column isotope dilution using liquid chromatography-chemical oxidation-isotope ratio mass spectrometry (ID-LC-CO-IRMS) has previously been suggested as a means to determine the purity of organic compounds; however, the lack of an uncertainty budget has prevented assessment of the utility this approach until now. In this work, the previously published ID-LC-CO-IRMS methods have not only been improved by direct gravimetric determination of the mass flow of 13C-labelled spike but also a comprehensive uncertainty budget has been established. This enabled direct comparison of the well-characterised ID-LC-CO-IRMS method to quantitative nuclear magnetic resonance spectroscopy (qNMR) for purity determination using valine as the model compound. The ID-LC-CO-IRMS and qNMR methods provided results that were in agreement within the associated measurement uncertainty for the purity of a sample of valine of (97.1 ± 4.7)% and (99.64 ± 0.20)%, respectively (expanded uncertainties, k = 2). The magnitude of the measurement uncertainty for ID-LC-CO-IRMS determination of valine purity precludes the use of this method for determination of purity by direct analysis of the main component in the majority of situations; however, a mass balance approach is expected to result in significantly improved measurement uncertainty.

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Direct Measurements of Small Polar Impurities in Gasoline Mixtures Using Molecular Rotational Resonance Spectroscopy

Applied Spectroscopy ◽

10.1177/0003702819859012 ◽

2019 ◽

pp. 000370281985901

Author(s):

Artressa L. Christophe ◽

Jalon T. Barnes ◽

Sylvestre Twagirayezu ◽

Aleksandr Mikhonin ◽

Matthew T. Muckle ◽

...

Keyword(s):

Polar Compounds ◽

Resonance Spectroscopy ◽

Rotational Spectrum ◽

Rotational Resonance ◽

Rotational Spectra ◽

Direct Measurements ◽

Commercial Gasoline ◽

Standard Linear ◽

Petroleum Analysis ◽

Ethanol In Water

This paper reports our efforts to determine whether rotational spectroscopy is a useful tool for petroleum analysis. These efforts include the use of a BrightSpec molecular rotational resonance (MRR) spectrometer, which operates in the 260–290 GHz frequency range, to record rotational spectra of small polar contaminants in commercial gasoline. The observed rotational spectra showed rich, but assignable, patterns due to the sensitivity of the MRR to only small polar compounds. Any interference from a complex hydrocarbon matrix, which in conventional chromatographic methods obscures signals from small polar contaminants, is nearly eliminated. In addition to the evident rotational spectrum of ethanol, the spectra of toluene, ethyl cyanide, and acetaldehyde have also been detected. A quantitative method for ethanol has been developed and demonstrated in this paper, whereas the specific analyses of the other polar impurities will be reported in the future. The validity of MRR to be used as an analytical instrument has been examined by constructing a standard linear curve using dilutions of ethanol in water. The linearity and percentage recovery parameters are satisfactory.

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