The NIDS® NPX4000 interfering protein removal/extraction kit enables the analyst to prepare coated nanoparticles for scavenging of interfering proteins prior to analysis. Interfering substances such as endogenous binding proteins, free drug molecules, blockers, immune complexes, and receptors can be removed from the sample using these coated nanoparticles. The process uses less binding reagent with greater binding capacity and can remove up to 1µg/mL of interfering proteins. Bioanalytical methods such as diagnostic, pharmacokinetic, pharmacodynamic, and immunogenicity assays may show improved accuracy and sensitivity after sample pretreatment using these extraction nanoparticles linked to a chosen binding reagent.