Quantitative Analysis of Powder Mixtures by Raman Spectrometry: the influence of particle size and its correction

Abstract

Particle size distribution and compactness have significant confounding effects on Raman signals of powder mixtures, which cannot be effectively modeled or corrected by traditional multivariate linear calibration methods such as partial least-squares (PLS), and therefore greatly deteriorate the predictive abilities of Raman calibration models for powder mixtures. The ability to obtain directly quantitative information from Raman signals of powder mixtures with varying particle size distribution and compactness is, therefore, of considerable interest. In this study, an advanced quantitative Raman calibration model was developed to explicitly account for the confounding effects of particle size distribution and compactness on Raman signals of powder mixtures. Under the theoretical guidance of the proposed Raman calibration model, an advanced dual calibration strategy was adopted to separate the Raman contributions caused by the changes in mass fractions of the constituents in powder mixtures from those induced by the variations in the physical properties of samples, and hence achieve accurate quantitative determination for powder mixture samples. The proposed Raman calibration model was applied to the quantitative analysis of backscatter Raman measurements of a proof-of-concept model system of powder mixtures consisting of barium nitrate and potassium chromate. The average relative prediction error of prediction obtained by the proposed Raman calibration model was less than one-third of the corresponding value of the best performing PLS model for mass fractions of barium nitrate in powder mixtures with variations in particle size distribution, as well as compactness.

The Effect of the Particle Size on the Fundamental Vibrations of the [CO32–] Anion in Calcite

“…Spectral intensities (infrared absorption and Raman intensity) are generally considered proportional to concentration by Boguer-Lambert-Beer Law or by other mathematical formulae derived from the fundamental law of quantitative spectroscopy. [3][4][5][6] However infrared spectra acquired from powdered calcite and other mineral species are known to undergo changes as a function of particle grain size. 2,7-9 The effect of particle size on the spectral resolution of the fundamental vibrations of the [CO3 2-] anion in calcite were identified in infrared emission studies and have been divided into three classes of behavior.…”

Raman spectroscopy explores molecular structural signatures of hidden materials in depth: Universal Multiple Angle Raman Spectroscopy

“…The scattering properties of the sample can be characterized by a single parameter l* corresponding to the transport length of the light in the medium, also defined as the photon path after which the photon direction is totally randomised23. The penetration depth of the light is therefore proportional to l*.…”

Raman-spectroscopy-based chemical contaminant detection in milk powder

“…Defined by unique spectral peak position(s) for each chemical component, Raman scattering provides a basis for qualitative analysis [3] . Meanwhile, the intensity of the unique spectral peak(s) provide basis for quantitative analysis of chemical contaminants in foods [4,5] . Chen et al 2012 reported that particle size influences the quantitative analysis of powder mixtures and used several methods for correction [5] .…”

“…Meanwhile, the intensity of the unique spectral peak(s) provide basis for quantitative analysis of chemical contaminants in foods [4,5] . Chen et al 2012 reported that particle size influences the quantitative analysis of powder mixtures and used several methods for correction [5] . The authors reported that the correction methods slightly decreased the prediction accuracy.…”