Hexatriacontane

Hexatriacontane was purchased from Sigma-Aldrich (St. Louis, MO, USA), and S.D. Fine Chemicals Ltd., Mumbai, India provided the HPLC grade chloroform and methanol (Mumbai, India). Triethanolamine and polyethylene glycol (PEG) were supplied by Sigma-Aldrich (St. Louis, MO, USA). Carbopol 934 was purchased from B.S. Goodrich in Cleveland, OH, USA. An additional agent used in the experiment was of analytical quality.

Five μL of a ribitol (Sigma-Aldrich, München, Germany) stock solution (4 mmol/L in water) was added to a volume of 1.5 mL of each extracted sample (Section 3.2) as internal standard. After evaporation of the solvent, 50 μL of a methoxyamine hydrochloride (Sigma-Aldrich) solution (20 mg/mL) in pyridine was added for derivatization and incubated at 60 °C for 1 h, or at 20 °C for an additional 9 h [47 (link)]. Subsequently, 50 μL of N-Methyl-N-(trimethylsilyl)trifluoroacetamide (Macherey-Nagel, Düren, Germany), supplemented with decane, pentadecane, nonadecane, octacosane, dotriacontane (each final concentration = 40 μmol/L) and hexatriacontane (final concentration = 20 μmol/L) (Sigma-Aldrich) was added to each sample for the calculation of the retention time index, and incubated at 40 °C for 1 h. The samples were transferred into 100 μL glass inserts of 1.5 mL vials and measured directly using GC-MS [47 (link)].