Size Exclusion Chromatography (SEC) on a semi-preparative scale (10 mg and more) was used to size-select ultrasmall gold nanoclusters (< 2 nm) from polydisperse mixtures. In particular, the ubiquitous byproducts of the etching process towards Au38(SR)24 (SR: thiolate) clusters were separated and gained in high monodispersity (based on mass spectrometry). The isolated fractions were characterized by UV/Vis spectroscopy, MALDI mass spectrometry and electron microscopy. Most notably, the separation of Au38(SR)24 and Au40(SR)24 clusters is demonstrated.