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Lipid hydroperoxides determination in milk‐based infant formulae by gas chromatography
Author(s) -
Lagarda María Jesús,
Mañez José Gabriel,
Manglano Pilar,
Farré Rosaura
Publication year - 2003
Publication title -
european journal of lipid science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.614
H-Index - 94
eISSN - 1438-9312
pISSN - 1438-7697
DOI - 10.1002/ejlt.200390071
Subject(s) - chemistry , acetic anhydride , gas chromatography , chromatography , mass spectrometry , methanol , pyridine , flame ionization detector , organic chemistry , catalysis
A simple gas chromatograph using a flame ionization detector and a polar capillary column method is proposed for determining hydroperoxides in the lipid fraction of milkbased infant formulas. Tricosanoic acid is used as internal standard. The method includes the following steps: a) the extraction of fat with chloroform/methanol (2:1, v/v), b) the reduction of hydroperoxide acids to hydroxide acids with hydrogen gas and palladium as a catalyst, c) the transmethylation to obtain the methyl esters with acetyl chloride and methanol/ hexane (4:1, v/v), and d) an acetylation with acetic anhydride/ pyridine (4:1, v/v) to obtain an acetoxy derivate of the hydroxide present. Two chromatography runs, before and after the acetylation step, are carried out. The decrease in the retention time observed after the acetylation process is the criterion used to detect the hydroperoxide. A gas chromatography‐mass spectrometry analysis is applied to confirm the conversion of hydroperoxide acids to the acetylated forms and to identify the specific hydroperoxide structures. The estimated precision expressed as relative standard deviation (12.1%) and the accuracy, estimated by recovery assays (105 ± 28.3%) confirm the analytical quality of the method. In the milk‐based infant formula analyzed after storage of 11 months at 22 °C, the total hydroxide found corresponded to C 18 . The gas chromatography‐mass spectra obtained after the acetylation step confirmed the presence of methyl 9‐ and 13‐acetoxyoctadecanoate/s, respectively, derived from the corresponding peroxides.