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DEFINITION This method is used for the determination of fatty acid esters of 2-chloropropane-1,3-diol (2-MCPD), 3-chloropropane-1,2-diol (3-MCPD) and glycidol in edible oils and fats; see also AOCS Official Methods Cd 29a-13 or Cd 29b-13. The sum of bound 3-MCPD and bound glycidol is determined as free 3-MCPD (Assay A). The addition of a dilute solution of sodium hydroxide or sodium methoxide in methanol releases free 3-MCPD and free glycidol by base catalysis. This reaction is stopped by the addition of an excess amount of an acidic chloride-containing salt solution. Under acidic conditions, free glycidol reacts with inorganic chloride to generate additional 3-MCPD and a small amount of 2-MCPD. Derivatization is completed by phenylboronic acid for the measurement by GC/MS. Bound 3-MCPD (Assay B) is released by a dilute solution of sodium hydroxide or sodium methoxide in methanol. This reaction is stopped by the addition of an excess amount of an acidic chloride-free salt solution (e.g., sodium sulphate, ammonium sulphate, sodium bromide). Under chloride-free acidic conditions, free glycidol does not generate additional 3-MCPD. SCOPE This method describes a procedure for the direct determination of 3-MCPD esters (bound 3-MCPD) and free 3-MCPD after alkaline-catalyzed ester cleavage and derivatization with phenylboronic acid. Furthermore, this method enables the indirect determination of glycidyl esters (bound glycidol) under the assumption that no other substances are present that react at room temperature with inorganic chloride to generate 3-MCPD. This method is applicable to solid and liquid fats and oils present as such or obtained by cautious extraction from processed fat- and oil-containing foodstuffs.