Analysis and Clinical Application of Polyunsaturated Fatty Acids in Human Serum Using One-step Extraction and Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Abstract

Omega-3 and omega-6 fatty acids are reported to alleviate various inflammatory reactions such as asthma, chronic obstructive pulmonary disease, rheumatoid arthritis, and inflammatory bowel disease. We have developed a new method for their quantitation in serum, utilizing ultra-high-performance liquid chromatography-electrospray ionizationtandem mass spectrometry (UHPLC-ESI-MS/MS) in multiple reaction monitoring (MRM) mode, under negative ionization. MRM transitions were detected for five omega fatty acids, as follows: α-linolenic acid, m/z=277.20→277.20; eicosapentaenoic acid, m/z=301.10→257.30; docosahexaenoic acid, m/z=327.00→283.15; arachidonic acid, m/z=303.20→259.25; docosapentaenoic acid, m/z=329.10→285.25. After comparing several different solvents, we selected butanol:methanol (1:1, v/v) as the optimal extraction solvent. Chromatographic separations were carried out using an Acclaim RSLC 120 C18 column (150×2.1 mm, 2.2 μm) at 40oC. For the mobile phase, solvent A consisted of water containing 5% acetonitrile and 5% methanol, and solvent B consisted of methyl tert-butyl ether:acetonitrile:methanol (10:20:70, v/v/v) containing 2.5 mM ammonium acetate. The calibration curve showed excellent linearity within the range of 0.01-20 μg/mL (R2=0.9996-0.9999). The analytical method was validated and shown to have excellent sensitivity (LOD; 0.001-0.005 μg/mL, LOQ; 0.01-0.2 μg/mL), making it suitable for targeted analyses of omega fatty acids. Recovery ranged from 78.0 to 103.9% (RSD 0.5-5.6%). This new method uses relatively small amounts of serum and extraction solvent and is expected to be suitable for analysis of various clinical specimens, such as plasma, urine, and cerebrospinal fluid.