“…Micro- and nanoparticles are of current interest for a range of applications in materials sciences, life sciences, and medicine, including, for example, DNA sequencing, fluorescence-based assays, sensors, in vivo imaging, drug delivery, and optoelectronic devices. − The key to better understand and control their materials properties and interactions with other molecules lies in the precise knowledge of the number, chemical nature, and spatial distribution of their surface functional groups. , Up-to-date methods for quantifying the number of surface functional groups include, for example, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), solid-state NMR, or isothermal titration calorimetry. − However, for determination of acidic or basic surface functional groups, potentiometry and conductometry are still among the most widely used methods, because they are relatively straightforward to implement and do not require highly sophisticated and specialized instrumentation. − As an alternative, colorimetric or fluorometric assays have been developed, which are faster and more sensitive but may suffer from certain artifacts if not properly validated. − …”