A method of detecting free flocculant polymer having a net charge present in an aqueous phase of a multi-phase substance is provided. The multi-phase substance comprises a solid phase, an organic phase, and the aqueous phase. The method comprises separating the solid phase from the multi-phase substance to form a dual phase top liquid comprising the organic phase and the aqueous phase; separating the organic phase from the dual phase top liquid, leaving the aqueous phase; combining the free flocculant polymer in the aqueous phase and a dye having an opposite net charge than that of the free flocculant polymer, thereby causing a spectroscopically observable change in the aqueous phase; and analyzing the aqueous phase via spectrometry to determine the concentration of the free flocculant polymer in the multi-phase substance.