This work reports on the resonance light scattering (RLS) technique for studying the interaction of humanserum albumin (HSA) with three opiates drugs (i.e. morphine (MO), oxycodone (OX) and thebaine (TH)).RLS is very sensitive to the interaction caused by weak binding forces such as intermolecular electrostaticattraction, hydrogen bonding, hydrophobic interaction, and aggregation interaction of biological macro-molecules. The results of this work showed that the investigated drugs, with similar chemical structures,have different affinities to interact with HSA and enhance its RLS signal in following order: MO > OX > TH.Furthermore, the results showed that using the proposed method, MO could be determined in the pres-ence of TH (up to ten-fold concentration ratio), OX (up to seven-fold concentration ratio) and both ofOX and TH (up to three-fold concentration ratio) in the concentration range of 0.1–10.0 g mL−1withdetection limit of 43 g L−1.
