Identification and quantitation of cis/trans C16:1 and C17:1 fatty acid positional isomers in German human milk lipids by thin-layer chromatography and gas chromatography/mass spectrometry

Trans fatty acids in human milk

“…Using the combination of Ag-TLC and GC the contents of trans-C16:1 have been determined in 27 German bovine milk fats exhibiting a mean content of only 0.13% (range: 0.05-0.25%) [6]. It could be demonstrated [6,18] that due to an overlap with C17 straight and branched fatty acids frequently too high trans-C16:1 contents had been obtained in former studies where no pre-separation by TLC was applied. In Tab [14].…”

Tracing carbon assimilation in endosymbiotic deep-sea hydrothermal vent Mytilid fatty acids by <sup>13</sup>C-fingerprinting

“…Aliquots of the PLFA or tFA mixture and of the MUFA, DUFA and PUFA fractions were derivatised further by a one step reaction into dimethyloxazolines (DMOX) to locate the unsaturations by GC-MS (Fay and Richly, 1991). We used a temperature gradient similar to the one used for FAME analyses, but since DMOX derivatives are less volatile (see also Precht and Molkentin, 2000) we increased the temperature of the isotherm plateaus at 135 • C, 170 • C and 195 • C for the temperature program described above, by 10 • C to 145 • C, 180 • C and 205 • C, respectively. The International Union of Pure and Applied Chemistry PLFA nomenclature used here is described by Guckert et al (1985): the (n−) notation indicates the position of the carbon-carbon double bond in the FA aliphatic chain starting from the methyl end carbon.…”

Conjugated linoleic acids and octadecenoic acids: Analysis by GC

“…However, an even better trans standard may be the trans fraction isolated from total milk fats by Ag + -TLC. Milk lipid has all the trans C18:1, C16:1 and C20:1 in well-recognizable and similar proportion; see representative GC chromatograms of all these three regions [6,7]. The cis isomers isolated from total milk lipids are equally valuable, but the concentration of the isomers is very unequal, dominated by ∆9c-C18:1 and ∆9c-C16:1.…”

“…Therefore, interferences of the C18:1 isomers would appear to be minimal. However, this is not the case in the C16:1 region which consists of a complicated mixture of saturated branched fatty acids (C17iso and C17anteiso), plus a spectrum of t-C16:1 and c-C16:1 isomers [6].…”