64205 2025 eng poster 0 -- -- -- Surface chemistry of engineered nanomaterials (NMs) plays a critical role not only in determining their interactions with the environment but also in their stability, safety, and functionality across diverse applications ranging from catalysis to biomedicine. Accurate quantification of surface functional groups (FGs) is therefore essential for quality control, risk assessment, and performance optimization.[1] However, many existing analytical techniques are either cost-intensive, require specialized instrumentation, or lack scalability for routine use. In this study, we present a comparative evaluation of potentiometric and optical titration as two simple, cost-efficient, and automatable methods for quantifying surface functional groups on a variety of surface-modified silica nanoparticles (SiO₂ NPs). These NPs were chosen as they are among the most frequently utilized engineered NMs in the life and material sciences. Potentiometric titration, based on pH monitoring during acid-base neutralization, offers a direct and label-free approach to determine the total amount of FGs. Optical titration provides a complementary method with potential for high-throughput screening. To examine the accuracy and robustness of our stepwise-optimized workflows and the achievable relative standard deviations (RSDs), measurements were performed by multiple operators in two laboratories. Method validation was conducted through cross-comparison with traceable, chemo-selective quantitative nuclear magnetic resonance spectroscopy (qNMR) and thermogravimetric analysis (TGA). A comparison with optical assays highlights the importance of measuring both quantities for comprehensive characterization of surface-modified NMs.[2] A combined NM surface analysis using optical assays and pH titration will simplify quality control of NM production processes and stability studies, and can yield large datasets for NM grouping in sustainable and safe(r)-by-design studies. eMRS Fall Meeting 2025 Warsaw, Poland 15.09.2025 publish Isabella Tavernaro P. Sander Elina Andresen U. Schedler Ute Resch-Genger eng uncontrolled Fluorescence eng uncontrolled Advanced material eng uncontrolled Synthesis eng uncontrolled Characterization eng uncontrolled Nano eng uncontrolled Particle eng uncontrolled Silica eng uncontrolled Surface analysis eng uncontrolled Validation eng uncontrolled qNMR eng uncontrolled Fluram assay eng uncontrolled Functional group eng uncontrolled Quantification eng uncontrolled Potentiometry eng uncontrolled Amino groups eng uncontrolled Fluorescamine eng uncontrolled Calibration eng uncontrolled Method comparison Analytische Chemie Ingenieurwissenschaften und zugeordnete Tätigkeiten 1 Analytische Chemie; Referenzmaterialien 1.2 Biophotonik Material Chemie und Prozesstechnik Chemische Charakterisierung und Spurenanalytik Datei im Netzwerk der BAM verfügbar ("Closed Access") Präsentation Advanced Materials