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• LIBS quantification of calcium in liquid infant formula. • Use of a rotatory wheel for liquid surface analysis through formation of thin films. • Linear regression with PLS successfully developed. • Calcium contents were predicted with good accuracy. The present work illustrates the potential of laser-induced breakdown spectroscopy (LIBS) for the direct analysis of liquid food products. The aim of the experiment was to predict calcium content in ready-to-feed infant formula. The analysis was performed by a LIBS system coupled to a liquid sample chamber with a rotatory wheel that presents the liquid to the laser beam as a thin film. Multivariate analysis with partial least squares regression (PLSR) was performed to correlate LIBS spectral data to reference calcium contents. The obtained PLSR model exhibited a good fit and linearity, as indicated by the coefficients of determination for calibration (R c 2) and cross-validation (R cv 2), with values of 0.96 and 0.89, respectively. The robustness of the calibration model was assessed by external validation showing a root-mean-square error of prediction of 6.45 mg 100 mL−1. These results demonstrated the potential of LIBS for real-time analysis of liquid food products. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) was employed to predict the sodium content of infant formula (IF) over the range 0.5–4 mg Na g −1 . Calibration models were built using partial least squares regression (PLS), correlating the LIBS spectral data with reference Na content quantified by atomic absorption spectroscopy (AAS). The main aim of this study was to demonstrate the ability of LIBS as a rapid tool for quantifying sodium in IF, but also to explore strategies concerning the acquisition and pre-processing of LIBS spectra. A range of different pre-processing techniques, measuring depths (repetition of laser shots) and accumulations were conducted and evaluated in terms of PLS performance. The best calibration model was developed using the third-layer spectra normalised by the H I 656.29 nm emission line, yielding a coefficient of determination (R 2 ) of 0.93, and root-mean-square errors (RMSE) of 0.37 and 0.13 mg g −1 for cross-validation and validation, respectively. [ABSTRACT FROM AUTHOR]

• LIBS, Raman, FT-IR were investigated to quantify calcium (Ca) content in INF. • Chemical references of calcium content in INF were obtained using AAS. • PLSR models developed based on LIBS and the data fusions of Raman and FT-IR spectra. • Feasibilities of LIBS, Raman and FT-IR for quantification of Ca in INF were demonstrated. Laser-induced breakdown spectroscopy (LIBS), Fourier transform mid-infrared (FT-IR) and Raman spectroscopy combined with chemometrics were investigated to quantify calcium (Ca) content in infant formula powder (INF). INF samples (n = 51) with calcium content levels (ca. 6.5–30 mg Ca/100 kJ) were prepared in accordance with the guidelines of Commission Directive 2006/125/EC. Atomic absorption spectroscopy (AAS) was used as the reference method for Ca content determination. To predict Ca content in INF samples, partial least squares regression (PLSR) models that developed based on LIBS, Raman and FT-IR spectral data, respectively. The model developed using LIBS data achieved the best performance for the quantification of Ca content in INF (R2 (cross-validation (CV))-0.99, RMSECV-0.29 mg/g; R2 (prediction (P))-1, RMSEP-0.63 mg/g). PLSR models that developed based on data fusion of Raman and FT-IR spectral features obtained the second best performance (R2CV-0.97, RMSECV-0.38 mg/g; R2P-0.97, RMSEP-0.36 mg/g). This study demonstrated the potential of LIBS, FT-IR and Raman spectroscopy to accurately quantify Ca content in INF. [ABSTRACT FROM AUTHOR]