Home⇛Annals of Tropical Research⇛vol. 48 no. 1 (2026)

Analytical Validation of a GC–MS Method Employing an In Situ Acid-Catalyzed Transmethylation for Fatty Acid Quantification in Aquaculture Biological Matrices

Nico G. Dumandan | Adonis A. Yanos | Andrei D. Dela Mar | Annie Cita T. Kagaoan | Al Jerome A. Magsino

 

Abstract:

Accurate fatty acid quantification in aquaculture feeds and biological tissues is essential for nutritional evaluation and lipid metabolism studies. In routine practice, GC–MS-based fatty acid analysis often relies on multi-step workflows involving lipid extraction followed by derivatization, which may increase analytical complexity and handling-related variability. To address these methodological challenges, a validated analytical workflow is reported for quantitative fatty acid profiling using in situ hydrochloric acid–catalyzed transmethylation coupled with gas chromatography–mass spectrometry (GC–MS). An established acid-catalyzed transmethylation reaction was employed directly within the sample matrix, eliminating any prior lipid-extraction step. Validation performed under ISO/Eurachem guidelines confirmed excellent linearity (R² > 0.99 for all analytes), high precision (intra-day RSD 1.72–8.69%, inter-day RSD 1.77–10.15%), and acceptable recovery (81.5–118.3%). Sensitivity was high, with LOD and LOQ values of 0.02–0.41μg -1 -1 mL and 0.07–1.35μg mL , respectively. Acquisition in selected-ion monitoring (SIM) mode improved signal-to-noise relative to full-scan, enabling reliable quantification of lowabundance polyunsaturated fatty acids. The workflow performed consistently across feed material, fish oils, and lyophilized tissue samples, with stable retention behavior and maintained ion-ratio fidelity. Collectively, this work provides the first ISO/Eurachem-validated demonstration that in situ HCl-catalyzed transmethylation supports extraction-free and analytically equivalent FAME quantification in complex matrices, establishing an eco-efficient and high-throughput platform for routine application in lipid chemistry and related biochemical investigations.



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