Simple and Robust UPLC-MS Method for Serum Arachidonic Acid with Potential Application in Clinical Settings

Arachidonic acid (AA) is a polyunsaturated fatty acid, an essential component of the brain membrane phospholipids. It is released into the bloodstream in response to various pathological conditions. Its potential as a biomarker for oxidative membrane damage determines the importance of its reliable quantification. Therefore, the aim of the current study was to develop a simple and robust LC-MS method that is easy to implement for routine testing of free arachidonic acid (AA) in human serum. The method included a simple two-step sample preparation procedure based on liquid–liquid extraction and protein precipitation, followed by AA analysis by UPLC coupled with PDA and QDa detectors. The ICH M10 guideline was followed for validation studies. The method demonstrated high selectivity and linearity with R2 = 0.9952 for solvent-based and R2 = 0.9979 for matrix-matched calibration. The LODs and LOQs were 0.046 µg/mL and 0.133 µg/mL, respectively. The accuracy and precision were between 6 and 14% RSD. No carry-over and matrix interferences were observed. The method was successfully applied to real serum samples, where AA concentrations ranged from 0.82 to 2.69 µg/mL, consistent with data of other studies. This method provides a reliable, reproducible, and rapid alternative for AA quantification in research and routine practice.