## 1 Introduction  
Vegetable oils (VOs) are an important food product in the daily diet. As well as having a relatively low cost, they contain essential nutrients that provide many benefits, including reducing the risk of cardiovascular diseases, improving metabolism, and providing a person with energy and nutritional components [1; 2; 3; 4]. Edible VOs are food products consisting primarily of the glycerides of fatty acids (FAs) and their accompanying substances, obtained exclusively from vegetable sources and containing at least 99% fat. The high biological value of VOs is due to the content of polyunsaturated FAs (linoleic acid C18:2 and linolenic acid C18:3), fat-soluble vitamins (A, D, E, K), phospholipids (lecithin) and carotenoids, including beta-carotene (provitamin A) [5; 6; 7; 8; 9; 10]. In recent years, the relevance of a healthy lifestyle has increased. The World Health Organization recommends reducing certain types of fats and oils (butter, ghee and lard) in favor of healthier oils such as olive, soybean, rapeseed (canola), maize, safflower and sunflower oils [11]. Kazakhstan is located in the middle of the Eurasian continent. Because of its particular climatic and geographical situation, certain types of VOs grow in the country. Kazakhstan's fat and oil industry is actively increasing the production of oilseeds not only within the country, but also abroad, due to the diversity of the raw fat and oil materials cultivated for local conditions. The fat and oil market of the country can be divided into raw materials markets, primary processing products and final products [12]. Kazakhstan's fat and oil industry is focused on the use of domestic raw materials, primarily the production of sunflower oil. The climate and soil conditions of Kazakhstan allow producers to grow various oilseeds that can successfully compete in international markets. This applies to both the traditional crops of Kazakhstan, such as sunflower, cottonseed and linseed, and those that currently occupy small areas but are actively developing, such as soybeans, rapeseed, safflower and other crops [13]. In 2020, a total of 484.8 thousand tons of VOs were produced. The main VO was sunflower (320.1 thousand tons) and rapeseed (68.8 thousand tons) oils, which accounted for more than 80% of the total production. Nevertheless, soybean, safflower, linseed and maize oils production increased by 47%, 62%, 79% and 86% in five years, respectively [14] (Figure 1). The domestic fat and oil market is diverse, and the volume of oil production is expanding, as a result of which, there is concern with regard to the authenticity of VOs. In addition, the market receives not only edible VOs, but also those technologically processed for food. The country's market is also filled with incoming imported fat and oil products. Given the rather complex chemical composition of VOs, there are problems with conducting a comprehensive examination of the authenticity of all types of VOs sold in the country's food markets [15]. A reliable way to determine the type of oil is to establish its chemical composition. The FA profile contains stable and informative characteristics by which the type of oil can be identified [16]. The analysis of FA profiles in food products requires the extraction of lipids from samples, followed by separation, identification and determination using various methods. Another important factor is the presence and ratio of the polyunsaturated FAs of the omega-6 and omega-3 groups, which perform vital functions and are part of the membrane structures of cells [2; 6; 8; 15; 17]. GC is one of the most effective and precise methods for solving the problem of identifying FA components, since this method is multifaceted and highly sensitive, and has a small budget for analysis [18; 19]. Various GC detectors, such as FPDs (flame photometric detectors), ECDs (electrolytic conductivity detectors), PIDs (photoionization detectors), FIDs (flame ionization detectors) and mass detectors (MS) have high sensitivity for detecting FAs.