Lipids Extraction and Separation

Introduction

Lipids represent a major class of biomolecules encompassing a wide range of distinct chemical structure, which are widely found in living organisms such as animals, plants and bacteria. Their various biochemical functions and potential commercial applications have greatly promoted the research of natural lipids by scientists. Before analysis and research of lipid samples can be commenced, it is necessary to extract the lipids from tissue matrices and free them of any non-lipid contaminants. However, the chemical and structural diversity of lipids and the cellular complexity of biological samples, such as body fluids, tissues, and cells, make efficient extraction of lipids quite challenging. Here, with a wealth of experience in lipids research, Alfa Chemistry will introduce several methods of lipids extraction and separation to accelerate your scientific research.

Common Methods

Today, more and more methods have been used for lipids extraction and separation. Some of them are shown in below.

• Classical methods (Bligh and Dyer and Folch methods): The Folch method and Bligh and Dyer method, published in 1957 and 1959, respectively, are considered gold standards for the extraction of lipids. The Folch method is using a 2:1 (v/v) solvent mixture of chloroform/methanol to extract lipid, followed by purification of the extracts with a salt solution (0.003 N CaCl₂ or MgCl₂, or 0.05 N NaCl or KCl). The method is generally preferred to extract lipids from solid tissue. The Bligh and Dyer method is a simple adaptation of the Folch method. The main differences between the two methods are the ratio of chloroform/methanol/water, the volume of the solvent system, assumption of amount of water in the sample and the presence or absence of salts in the added water fraction. Fig. 1 briefly depicts these two methods^[1].

Fig. 1. Comparison of Bligh and Dyer method and Folch method.

• Modified Bligh and Dyer and Folch methods: Bligh and Dyer and Folch Methods are using toxic chloroform/methanol solvent to extract lipids. To remedy this shortcoming, Hara and Radin extracted lipids from mouse brain tissue using a mixture of N-hexane/isopropanol (3:2 v/v). Subsequently, Smedes used the mixed solvent of isopropanol/cyclohexane/water (8:10:11 v/v/v) to extract lipids from marine biological tissue. In addition, Axelsson and Gentili developed a faster single-step procedure for the extraction of total lipids from green microalgae, utilizing biomass (300 mg of wet microalgal paste or 30 mg in dry weight), dispersion in 10 mL solvent system (chloroform/methanol, 2:1, v/v), followed by addition of 0.73% NaCl water to produce a 2:1:0.8 system of chloroform/methanol/water (v/v/v), which overcomes the shortcoming of Bligh and Dyer and Folch Methods that require multi-step operation^[1].
• Soxhlet extraction: In this method, the sample is dried and ground into small particles and then placed with a porous cellulose cannula in an extraction chamber, which is suspended above a heated flask containing the solvent. The solvent is evaporated under heating conditions and subsequently converted to liquid when it enters the condenser and finally enters the extraction chamber containing the sample for lipids extraction. Soxhlet extraction provides a high yield of lipids. However, lipid oxidation may occur due to continuous heating^[2].
• Supercritical CO₂ extraction (SCE): SCE is the process of extracting lipids from the biological matrix by using supercritical CO₂ as the extracting solvent. As properties of CO₂ can be altered by varying the pressure and temperature, SCE offers selective extraction of lipids. SCE yields good recoveries for non-polar lipids, but polar lipids may remain partially unextracted because of their lower solubility in this fluid. The adding co-solvent such as ethanol and methanol can effectively increases the extraction yield of polar lipids.
• Accelerated solvent extraction (ASE): ASE, also known as pressurized fluid extraction (PFE), is a method that uses common solvents at high temperature and pressure to improve the extraction yield of a target substance from a sample matrix. During lipid extraction, high pressure can make the solvent highly permeable in the sample, while high temperature makes the lipids have higher solubility and higher diffusion rate in the solvent. The ASE has the advantages of automated and rapid, low consumption of solvents and commercially available^[2].
• Solid-phase extraction (SPE): SPE generally performed using small columns packed with hydrophobic, polar, or ion exchange sorbents. These columns selectively hold the desirable lipids through polar, hydrophobic, or ionic interactions while undesirable compounds pass through.
• Others: Microwave-assisted extraction and ultrasound assisted extraction also have been developed in lipids extraction.

As a leading global supplier of lipids, Alfa Chemistry delivers a wide range of high-quality lipids and offers superior lipid-related services. For over many years, Alfa Chemistry has been working closely with the biochemical and pharmaceutical industries to provide quality solutions. Whether you need lipids for research or want to our experience and services to assist your research tasks, we have got you covered.

References

1. Saini R. K., et al. Advances in lipid extraction methods—A Review[J]. International Journal of Molecular Sciences, 2021, 22(24): 13643.
2. Donato P., et al. Separation of lipids[M]. Liquid chromatography. Elsevier, 2017: 201-243.