2.3. Ethyl carbamate analysis in wine 2.3.1. Chemicals and materials Extrelut NT 20 columns (they contain a mixture of diatom resin and Naci), Uvasol n-pentane (for spectrometry), and ethanol (abso lute, pro analysi) were purchased from Merck (Darmstadt, Ger many). Diethyl ether (for spectrometry) from Vetec Quimical Sigma-Aldrich (Duque de Caxias, Brazil), ethyl carbamate (98.5%) from Dr Ehrenstorfer (Augsburg, Germany), and ethyl-ds carba- mate (99%; isotopic purity 98 atom D) from Sigma-Aldrich (St. Louis, USA). Ultra-pure water (Milli-Q system) was used through out to prepare solutions.