Quantitative Determination of Isostearic Acid Isomers in Skin Creams by GC-MS-SIM

Exploring the fatty acids of vernix caseosa in form of their methyl esters by off-line coupling of non-aqueous reversed phase high performance liquid chromatography and gas chromatography coupled to mass spectrometry

“…The shortest retention time was found for 12:0 (because it contains one carbon less) while i13:0 and a13:0 marked retention time #2 and #5 in this group of C 12 being the longest carbon chain. In agreement with previous measurements of isostearates [29], the anteiso-congener was the last eluting monomethyl-branched homolog (Table 1). We also took advantage of plotting the logarithms of the GC retention times (log t R ) against the length of the longest chain [3] [34].…”

“…Potassium tert-butoxide in THF (20%, 0.1 mL) and 3-hydroxymethylpyridine (0.2 mL) was added and the solution was mixed and kept for 30 min at 40 • C. After cooling to room temperature 2 mL saturated NaCl solution was added and the picolinyl esters were extracted three times with 2 mL n-hexane. The volume of the n-hexane phase was adjusted to 1 mL and analyzed by GC/EI-MS [27][28][29].…”