A comparison of gas-phase electrophoresis (nES GEMMA instrumentation), nanoparticle tracking analysis (NTA) and a light scattering setup (SALD) for the characterization of polymer size standards V. U. Weiss, Vienna/AUT, S. Steinberger, Vienna/AUT, M. Marchetti-Deschmann, Vienna/AUT Assoc. Prof. Dr. Victor U. Weiss, TU Wien, Getreidemarkt 9/164, 1060 Vienna/AUT Research on nanoparticles in general and polymers in the sub-micrometer range in particular has increased lately due to their environmental impact and associated potential health risks. However, size and particle number determination in the nm size range with high throughput are challenging. In this context, we focused on gas-phase electrophoresis on a nano electrospray gas-phase electrophoretic mobility molecular analyzer (nES GEMMA) also known as nES differential mobility analyzer (nES DMA). With such an instrument analytes are electrosprayed from a volatile electrolyte solution. Drying of nES droplets and concomitant charge equilibration in a bipolar atmosphere is followed of size separation of singly-charged analytes in a high laminar sheath flow of ambient, filtered air and a tunable electric field applied in an orthogonal direction. [1] nES GEMMA offers the possibility of number-based detection of surface-dry nanoparticles in the single-digit nm-size range up to several hundred nm diameter in accordance with recommendations of the European Commission for nanoparticle characterization (updated version 2022/C 229/01, June 10th, 2022). Commercially available, well-defined polystyrene (PS) spheres were applied as size standards. Obtained results from gas-phase electrophoresis were compared to nanoparticle tracking analysis (NTA) and laser diffraction (SALD) data. In this context it is noteworthy that gas-phase electrophoresis results in surface-dry particle diameter values, whereas NTA and SALD yield hydrodynamic particle diameters. Furthermore, nES GEMMA is capable of detecting nanoparticles down to roughly 2 nm surface-dry particle diameter, whereas hydrodynamic diameter based techniques are often limited to detect particles below approx. 50 nm diameter. Furthermore, nES GEMMA revealed subpopulations of an exemplary bimodal analyte distribution obtained upon mixing of two differently sized PS standards. NTA and SALD failed to resolve the corresponding peaks. However, it is of note that NTA and SALD in contrast to nES GEMMA cover a broader size range – up to the low µm and mm scale. Furthermore, NTA and SALD do not rely on the application of a volatile electrolyte solution, unlike gas-phase electrophoresis. Although all of the considered methods are simple to use, proper training and knowledge of the instrumentation and settings must be considered to generate good and unbiased data. The choice of one of the three techniques for nanoparticle characterization must be made in the context of each individual analytical question. Literature: [1] S. L. Kaufman, Anal. Chem., 1996, 68, 11.