Evaluation of low-field nuclear magnetic resonance spectrometry for at-line process analysis

D. Littlejohn, A. Nordon, C.A. McGill

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

A low-field medium-resolution NMR spectrometer, with an operating frequency of 29 MHz for 1H, has been developed for use in process analysis. The information that is attainable at this field strength has been investigated with the use of samples from a wide range of applications including the qualitative monitoring of a benzene production process, the estimation of the average ethoxy chain length in nonyl phenol ethoxylates, and the determination of strong acid concentrations. At low field, the spectra of multi-component samples often exhibit overlapping peaks, so multivariate calibration methods are necessary for quantitative analysis. Simulated data have been used to illustrate the effects of signal-to-noise ratio (SNR), resolution, and line shape on the predictive ability of partial least-squares (PLS) calibration routines, with SNR shown to have a greater impact than resolution on accuracy and precision. PLS calibration models were applied successfully in the analysis of samples from a methacrylamide process and a simulated esterification reaction. The accuracy (<5%) and precision (<3%) were generally good for components at concentrations >1-5% w/w.
Original languageEnglish
Pages (from-to)75-82
Number of pages8
JournalApplied Spectroscopy
Volume56
Issue number1
DOIs
Publication statusPublished - 2002

Fingerprint

Spectrometry
Nuclear magnetic resonance
Calibration
nuclear magnetic resonance
evaluation
Signal to noise ratio
signal to noise ratios
spectroscopy
Esterification
Benzene
Chain length
phenols
quantitative analysis
Phenols
line shape
Spectrometers
field strength
benzene
spectrometers
acids

Keywords

  • NMR spectrometry
  • process analysis
  • partial least-squares

Cite this

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abstract = "A low-field medium-resolution NMR spectrometer, with an operating frequency of 29 MHz for 1H, has been developed for use in process analysis. The information that is attainable at this field strength has been investigated with the use of samples from a wide range of applications including the qualitative monitoring of a benzene production process, the estimation of the average ethoxy chain length in nonyl phenol ethoxylates, and the determination of strong acid concentrations. At low field, the spectra of multi-component samples often exhibit overlapping peaks, so multivariate calibration methods are necessary for quantitative analysis. Simulated data have been used to illustrate the effects of signal-to-noise ratio (SNR), resolution, and line shape on the predictive ability of partial least-squares (PLS) calibration routines, with SNR shown to have a greater impact than resolution on accuracy and precision. PLS calibration models were applied successfully in the analysis of samples from a methacrylamide process and a simulated esterification reaction. The accuracy (<5{\%}) and precision (<3{\%}) were generally good for components at concentrations >1-5{\%} w/w.",
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Evaluation of low-field nuclear magnetic resonance spectrometry for at-line process analysis. / Littlejohn, D.; Nordon, A.; McGill, C.A.

In: Applied Spectroscopy, Vol. 56, No. 1, 2002, p. 75-82.

Research output: Contribution to journalArticle

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AU - Littlejohn, D.

AU - Nordon, A.

AU - McGill, C.A.

PY - 2002

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AB - A low-field medium-resolution NMR spectrometer, with an operating frequency of 29 MHz for 1H, has been developed for use in process analysis. The information that is attainable at this field strength has been investigated with the use of samples from a wide range of applications including the qualitative monitoring of a benzene production process, the estimation of the average ethoxy chain length in nonyl phenol ethoxylates, and the determination of strong acid concentrations. At low field, the spectra of multi-component samples often exhibit overlapping peaks, so multivariate calibration methods are necessary for quantitative analysis. Simulated data have been used to illustrate the effects of signal-to-noise ratio (SNR), resolution, and line shape on the predictive ability of partial least-squares (PLS) calibration routines, with SNR shown to have a greater impact than resolution on accuracy and precision. PLS calibration models were applied successfully in the analysis of samples from a methacrylamide process and a simulated esterification reaction. The accuracy (<5%) and precision (<3%) were generally good for components at concentrations >1-5% w/w.

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