Chromatographic analysis of Fatty Acids composition in refined Hemp Seed Oils

Abstract

Hemp seed oil is well-known for its nutritional, pharmaceutical and cosmetic properties because of its perfectly balanced content of fatty acids. This study aims to qualify and quantify the fatty acids content in hemp seed oils sold on the market. A method of separation, identification and further quantification of fatty acids using a combination of TLC, FID-GC and GC-MS was developed. For the preparation of fatty acid methyl esters, two acid catalysed derivatization techniques including sulfuric acid-methanol and boron trifluoride-methanol were compared. The solvent system of hexane: diethyl ether: acetic acid (40:20:0.5, by volume), coupled with 20% ammonium bisulfate solution as a detecting reagent, exhibited a satisfactory FAME fractionation on TLC. GC analysis was carried out using a high polar BPX-70 column and methyl behenate acid (C23:0) as an internal standard. Both detectors, FID and MS, showed good peak resolution and acceptable linearity under optimum analytical conditions (R2 >0.99) in a concentration range of 26-417 µg/ml. Considering speed and the GC response, the method using boron trifluoridemethanol was found to be more efficient than the formation of FAMEs in sulfuric acid by refluxing for 4 hrs. Finally, using the developed method, the characterisations of fatty acids compositions in % of total content in oil sample were obtained successfully. Essential fatty acid, namely linoleic acid (18:2 n-6, 51%) and α-linolenic acid (18:3 n-3, 17%) were found predominant in the ratio of 3:1. The content of oleic acid was approximately 12%, while 20% of saturated fatty acid was found in hemp seed oil.