Recent publications have utilized multiwavelength transmission spectroscopy (MWT) to quantify particle sizes, particle mixtures and the effects of coating in protein systems. In this work, the limits of detection achieved using MWT spectroscopy are tested using NIST (National Institute of Standards and Technology) traceable polystyrene and glass standard particles as surrogates for contaminants or aggregates in solutions of bovine serum albumin. A range of concentration thresholds have been determined by leveraging the wavelength-dependent properties of the complex refractive indices of each material. These results indicate that MWT spectroscopy is a sensitive and effective means for the measurement of particulates (inherent as well as foreign) in protein systems.