Sp 2560 fused silica capillary column

Preparation of methyl esters of fatty acids and determination by capillary gas chromatography (Agilent 7890A system, Agilent Technologies, Santa Clara, CA, USA) equipped with a flame ionization detector (FID) and a SP-2560 fused-silica capillary column (100 m × 0.25 mm × 0.20 µm film thickness) were performed following official procedures (ISO12966-2, ISO12966-4) [13 ,14 ] at the Institute of Food Technology (FINS) of the University of Novi Sad, Serbia. A methyl ester standard mix of 37 fatty acids, Supelco 37 FAME mix (Supelco, Bellefonte, PA, USA) was used as an internal standard for the analysis of each sample. Results were expressed as percentages of total FA.

To perform a FA transmethylation analysis of substrate and larval extracts, a base-catalyzed procedure reported by Christie (1982 (link)) and modified by Chouinard et al. (1999 (link)) was used. The methyl esters were quantified by gas chromatograph (Agilent technologies, model 5890) fitted with an SP-2560 fused silica capillary column (100 m × 0.25 mm i.d. × 0.2 µm film thickness, Supelco, Inc., Bellefonte, PA, USA). The carrier gas, helium, was set at a constant pressure of 180 kPa, splitting flow of 50 mL/min, and injection volume of 1 µl. In column parameters, the initial temperature of the column was maintained at 170 °C for 15 min; then, with an increase of 5 °C/min, it was brought up to 240 °C. The total execution time was 64 min. By comparing the retention times of commercial standard containing 37 methyl esters of FAs (Merck Millipore, Burlington, MA, USA), FA peaks were identified. The retention times of the CLA isomers were controlled by the elution of commercial standards (Larodan AB-SE-171 65 Solna) of these FAs. The area of each individual FA identified in the sample was quantified by percentage calculation on the total area of the eluted peaks.