Spectroscopic analyses of complex mixtures within a fluid phase can oftentimes be complicated by spectral overlap, making it difficult to analyze for each constituent therein. Methods for analyzing a treatment fluid can comprise: providing a treatment fluid comprising a fluid phase and one or more constituents therein; exposing the treatment fluid to electromagnetic radiation in a spectral region where the fluid phase optically interacts with the electromagnetic radiation, so as to acquire a spectrum of the fluid phase; analyzing the spectrum of the fluid phase to determine at least one property of the treatment fluid, the at least one property of the treatment fluid being selected from the group consisting of a concentration of at least one constituent in the treatment fluid, at least one characteristic of the treatment fluid, and any combination thereof; and introducing the treatment fluid into a subterranean formation.