Mineral flotation is a particle separation process based on selective collection on the surface of bubbles leading to formation of bubble-particle aggregates. The separation is driven by natural or induced hydrophobicity of exposed mineral areas on the particle surface. Performance depends on the size range of the bubble population, which in most cases is controlled by addition of frothers. Measurement of frother concentration would help achieve this control objective. A previously developed colorimetric technique suitable for on-site use has been refined to increase analysis rate and reproducibility, particularly for low-solubility frothers. The refinements include the sample preparation procedure, wavelength range for spectra collection, and criteria for selecting calibration standard concentrations and wavelengths. The refined technique is demonstrated to be robust, reliable, and accurate, with a daily analysis rate up to 20 samples while remaining suitable for on-site analyses. (C) 2016 Published by Elsevier Ltd.