Spectrophotometric determination of Rare Earth Elements in aqueous nitric acid solutions for process control

[Display omitted] •Spectrophotometric determination of Rare Earth mixtures in HNO3 is studied.•Reliable models for quantification of Nd and Pr are constructed.•Models for semi-quantitative analysis of Ce are established.•Models’ performances are analyzed in out-of-control cases.•The predictability of the PLS and MCR–ALS models is compared. Noninvasive analytical control is of special interest for the complicated and hazardous production processes. On-line monitoring provides a unique opportunity to determine critical concentrations rapidly and without serious risks to operating personnel and the environment. Models for quantitative determination of concentrations of Rare Earth Elements in complex mixtures in nitric acid serve for these purposes. Here, the feasibility of simultaneous determination of cerium, praseodymium, and neodymium using the whole UV–vis spectroscopic range, together with chemometric data processing, is studied. The predictability of two chemometric techniques, partial least squares regression and correlation constrained multivariate curve resolution–alternating least squares are compared. Models’ performances are analyzed in out-of-control cases.