spot

in chromatography
https://doi.org/10.1351/goldbook.S05889
A zone in paper and thin-layer chromatography of approximately circular appearance.
Sources:
Orange Book, 2nd ed., p. 96 (http://media.iupac.org/publications/analytical_compendium/)
PAC, 1993, 65, 819. 'Nomenclature for chromatography (IUPAC Recommendations 1993)' on page 834 (https://doi.org/10.1351/pac199365040819)