Giorgis Isaac, ¹ Michael D. Jones, ¹ Besnik Bajrami, ¹ Wassim Obeid, ² James Langridge, ³ Patrick Hatcher ²
1 Waters Corporation (Milford, MA, USA)
2 Ou Daoming University (Norfolk, VA, USA)
3 Waters Corporation (Manchester, UK)

Application Advantages â–  Demonstrate the separation of multiple free fatty acids (FFA) based on chain length and number of double bonds
â–  No need for derivatization, simpler and faster sample preparation can be achieved to avoid interference. â–  Organic solvent extract can be directly injected into the system, saving time and cost per analysis. â– Chromatographic separation can be completed in three minutes. 10 times faster than GC/MS â–  Unlike GC/MS, UPC ² ® makes it easy to analyze very volatile very long chain fatty acids (>24 carbon atoms)

Waters Solutions
ACQUITY UPC ^{2 TM} System
TransOmicsTM Informatics Software
Xevo® G2 QTof mass spectrometer
ACQUITY UPC ² HSS Column

Keywords <br> free fatty acids, together with ultra high Chromatography, UPC ^2, TransOmics, time of flight mass spectrometry, UPC ² / MS / MS

INTRODUCTION <br> Free fatty acids and fatty acids that make up complex lipids play a key role in metabolism – as the main metabolic fuel (storage and transport energy), an essential component of all cell membranes, and gene regulators. In addition, dietary lipids provide polyunsaturated fatty acids, which are precursors to powerful topical metabolites such as eicosanoids. Common animal and plant derived fatty acids are even chains with 16 to 24 carbon atoms per chain and 0 to 6 double bonds. But there are countless exceptions in nature. In fact, there are even odd carbons and even carbon fatty acids of nearly 100 carbon atoms. In addition, the double bonds may be in the cis (Z) and trans (E) configurations, and may have various other structural features including branching points, rings, oxygen-containing functional groups, and the like.

The fatty acid chain may contain one or more double bonds (unsaturated fatty acids and polyunsaturated fatty acids having a cis (Z) or trans (E) configuration) at a specific site, or may be fully saturated. The LIPIDMAPS fatty acid system nomenclature uses "∆" to indicate the position of the double bond relative to the carboxyl group ¹ . The fatty acid structure contains a methyl group at one end of the molecule (designated Omega, ω) and a carboxyl group at the other end. The carbon atom near the carboxyl group is called alpha carbon, and the next carbon atom is called beta carbon. Typically, the letter "n" is also used instead of ω to indicate the closest double bond position ² to the methyl end. Figure 1 shows the structure of different linear fatty acids.

Separation of free fatty acids (FFA) from biological materials is a complex task that must be taken care of to prevent or minimize the effects of hydrolases. After separation is complete, fatty acids can be analyzed by typical chromatographic methods, including gas chromatography/mass spectrometry (GC/MS) and liquid chromatography-tandem mass spectrometry (LC/MS/MS). However, these methods have their own shortcomings.

For example, the GC method requires the derivatization of fatty acids for hydrolysis and conversion to methyl esters. This process is not only time consuming, but also carries the risk of fatty acid rearrangement during derivatization, making it impossible to determine whether the ester formed is from FFA or Complete complex lipids. Furthermore, for low volatility very long chain fatty acids with high molecular weight (>C24), GC/MS analysis is problematic even after fatty acid methyl ester (FAME) derivatization.

The UPC ² /MS FFA analysis described in this article is a simple and fast method that significantly reduces analysis time compared to other technologies such as GC/MS that require FAME derivatization. In addition, lipid-containing organic layer extracts can be directly injected into the system, compatible with reversed-phase LC methods without solvent exchange.

To download the full application note, please click: http://?cid=511436&lid=134753626&locale=zh_CN

Veterinary Drugs

Veterinary Drugs: refers to substances (including medicated feed additives) used to prevent, treat, diagnose animal diseases or purposefully regulate animal physiological functions.

Veterinary drugs mainly include: serum products, microecological products, Chinese herbal medicines, proprietary Chinese medicines, chemicals, antibiotics, and topical pesticides, disinfectants, etc.