Transmittance spectrophotometry was used to monitor copper, cobalt and zinc in solution in laboratory
experiments. The samples simulated plant conditions encountered on the Skorpion zinc mine in Namibia
and were prepared using a simplex centroid mixture design. Principal component, partial least squares
and support vector regression models were calibrated from visible and near infrared absorption spectra.
All models could accurately estimate the concentrations of all the metals in solution. Although these
models were affected by nickel contamination, the Cu models were less sensitive to this contamination
than the Co and Zn models. Likewise, elevated temperatures led to degradation of the calibrated models,
particularly the Zn models. The effects of these conditions could be visualized by a linear discriminant
score plot of the spectral data.