Practical Guide and Best Practices for Diffusion NMR Processing With GNAT.

Diffusion-NMR, including diffusion-ordered spectroscopy (DOSY), is a powerful technique for measuring self-diffusion and inferring molecular size, shape, aggregation, and intermolecular interactions in solution. Its noninvasive nature and ability to separate components in complex mixtures have made DOSY widely used across chemistry, biochemistry, and materials science. However, accurate and reproducible diffusion measurements depend not only on careful experimental design but also on robust, transparent, and consistent data processing. Despite the growing adoption of diffusion-NMR, widely adopted protocols, practical tutorials, and broadly accepted guidelines for DOSY data analysis remain limited, contributing to variability in reported diffusion coefficients and reduced comparability between studies. The General NMR Analysis Toolbox (GNAT) is a free, open-source platform for visualizing and analyzing diffusion-NMR data. In this article, we present a clear, step-by-step guide to processing diffusion-NMR data with GNAT, emphasizing best practices, quality control, and common pitfalls. The workflow covers data import, preprocessing (including baseline/phase considerations and signal selection), diffusion fitting and model choice, validation of results, and recommendations for reporting key parameters and uncertainty. Although written with new users in mind, this guide also serves as a reference for experienced practitioners seeking greater consistency and rigor in DOSY analysis. By promoting standardized, reproducible workflows and encouraging the use of open-source tools, this work aims to improve the transparency, quality, and comparability of diffusion-NMR studies.