Monitoring of a second‐order reaction by electronic absorption spectroscopy using combined chemometric and kinetic models

Abstract

This paper reports the application of 11 methods for obtaining kinetic constants from a second-order reaction, that between phenylhydrazine and benzophenone. In this type of reaction the number of absorbing species is lower than the number of steps in the reaction minus one, resulting in a rankdeficient response matrix. The methods used include traditional univariate curve fitting, classical least squares using previously recorded pure spectra, alternating least squares methods with both kinetic and non-negativity constraints, and target-testing methods using principal component scores. An additional recently proposed method based on difference spectra is also examined, suitable for any single-step closed reaction. The methods that performed best were difference spectra, kinetically constrained alternating least squares, and target-testing approaches. Limitations of the traditional methods are described.

UV‐Visible Spectroscopy for On‐Line Analysis

“…The pharmaceutical industry, driven by the FDA ' s PAT initiative, can be seen as a forerunner. This is refl ected by the observation that many references in this chapter are (co -) authored by representatives from pharmaceutical companies like Glaxo Wellcome 21,29 and GlaxoSmithKline, 8,10,36,39,40 Astra Zeneca, 19,38 Novartis 28 and Eli Lilly. 18 As with other spectroscopic techniques, UV -vis spectroscopy can readily be used in lab -based R & D. The implementation as process monitors, scanning for deviations from the set state, is certainly an added value and low in maintenance requirements.…”

“…On the other hand, the difference beween absorbances becomes dominated by noise close to the isosbestic points, which proved computationally challenging in a study by Thurston et al 10 There, those areas were excluded from the computation.…”

Near Infrared Spectroscopy for Polymer Research, Quality Control and Reaction Monitoring

“…52 For readers who would like to get more detailed information about chemometrics, a multitude of literature is available. [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70] Near infrared spectroscopy for polymer research A literature search using the SciFinder database of the American Chemical Society (ACS)� shows an increase in the number of publications dealing with NIR spectroscopy and polymers ( Figure 2)�. From 1960-1980 only three papers appeared and from 2000-2006 more than 160 manuscripts were published.…”

Application of Chemometrics Methods with Kinetic Constraints for Estimation of Rate Constants of Second Order Consecutive Reactions

“…[5][6][7][8][9][10][11] Only a limited number of studies include the second order reactions of the form U + V → W, [12][13][14] which are industrially important. Second order consecutive reactions,…”