Quantitative assessment of copper proteinates used as animal feed additives using ATR-FTIR spectroscopy and powder X-ray diffraction (PXRD) analysis

• Published in: Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment Chemistry, analysis, control, exposure & risk assessment, 2017-08, Vol.34 (8), p.1344-1352
• Main Authors: Cantwell, Caoimhe A., Byrne, Laurann A., Connolly, Cathal D., Hynes, Michael J., McArdle, Patrick, Murphy, Richard A.
• Format: Article
• Language: English
• Subjects: Absorption spectra; Amino acids; Animal feed; Animal Feed - analysis; Animals; ATR-FTIR; Band spectra; bioplex; Calibration; Complex formation; Complexation; Coordination compounds; copper; Copper - analysis; Crystal structure; Diagnostic systems; Diffraction; Feed additives; Food additives; Food Additives - analysis; Fourier transforms; Hydrolysates; Infrared spectroscopy; Linearity; Mathematical models; Mean square errors; Methods; Multivariate analysis; Powder; Powder Diffraction; Prediction models; proteinates; Proteins - analysis; PXRD; quant; Reflectance; Root-mean-square errors; Solid state; Spectroscopic analysis; spectroscopy; Spectroscopy, Fourier Transform Infrared; Statistical analysis; the unscrambler; X-ray diffraction; X-rays
• ISSN: 1944-0049; 1944-0057
• DOI: 10.1080/19440049.2017.1342144

The aim of the present work was to establish a reliable analytical method to determine the degree of complexation in commercial metal proteinates used as feed additives in the solid state. Two complementary techniques were developed. Firstly, a quantitative attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic method investigated modifications in vibrational absorption bands of the ligand on complex formation. Secondly, a powder X-ray diffraction (PXRD) method to quantify the amount of crystalline material in the proteinate product was developed. These methods were developed in tandem and cross-validated with each other. Multivariate analysis (MVA) was used to develop validated calibration and prediction models. The FTIR and PXRD calibrations showed excellent linearity (R 2  > 0.99). The diagnostic model parameters showed that the FTIR and PXRD methods were robust with a root mean square error of calibration RMSEC ≤3.39% and a root mean square error of prediction RMSEP ≤7.17% respectively. Comparative statistics show excellent agreement between the MVA packages assessed and between the FTIR and PXRD methods. The methods can be used to determine the degree of complexation in complexes of both protein hydrolysates and pure amino acids.