The accurate and sensitive detection of fatty acids (FAs) in biological samples is essential for advancing lipidomics and metabolic research. Traditional methods, such as gas chromatography coupled with electron-capture detection of pentafluorobenzyl esters, offer high sensitivity but require specialized equipment and complex sample preparation. In contrast, liquid chromatography–electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) has become a dominant platform due to its compatibility with diverse matrices and direct infusion capabilities. However, native FAs exhibit suboptimal ionization efficiency and limited fragmentation in negative ion mode, restricting their analytical utility.
To address these limitations, we developed a charge reversal derivatization strategy using N-(4-aminomethylphenyl)pyridinium (AMPP), which transforms the carboxylic acid group into a permanently charged amide derivative. This modification enables analysis in positive ion mode, where ionization efficiency is significantly enhanced. The resulting AMPP amides demonstrate exceptional sensitivity—over 60,000-fold greater than underivatized FAs analyzed in negative ion mode. This dramatic improvement is attributed to the stable positive charge that facilitates efficient ESI and robust fragmentation patterns during CID.
The method was optimized for use with reverse-phase LC columns, employing a gradient elution system with water and acetonitrile containing formic acid. A total of 37 FA molecular species, including saturated, monounsaturated, and polyunsaturated forms, were successfully resolved within a 15-minute run. Each analyte exhibited distinct retention times and unique MS/MS transitions, enabling confident identification. Key product ions, such as m/z 239 derived from cleavage between C3 and C4, were observed across all FA classes, providing a universal detection channel. Additionally, higher-mass fragment ions specific to individual species—such as m/z 295 for oleic acid and m/z 323 for vaccenic acid—enhanced analytical specificity by distinguishing structural isomers that co-elute.
Validation studies using commercial mouse serum revealed consistent detection across multiple runs. Intra-assay precision (n = 5) averaged below 4% coefficient of variation (CV), while inter-assay precision (n = 6 independent extractions) remained under 6% CV. Quantification limits were determined at 50–100 femtograms on-column, demonstrating suitability for trace-level analysis. Calibration curves showed excellent linearity over four orders of magnitude, confirming reliable quantitation across dynamic ranges.
Sample preparation involved a simple two-phase extraction with isooctane, effectively isolating free FAs from serum proteins and lipoproteins.Efavirenz Protocol All glassware and reagents were rigorously cleaned via oven baking and solvent distillation to minimize background contamination, particularly for low-chain-length FAs (C12–C18).UiO 66 Formula Derivatization was performed under mild conditions (60°C, 30 min) using EDCI/HOAt activation, ensuring complete conversion without degradation.PMID:34435735 Excess reagents were removed via pre-column diversion, preventing source fouling and maintaining instrument stability.
The use of deuterated internal standards (e.g., d8-AA, d17-oleic acid) enabled accurate absolute quantification by correcting for matrix effects and ionization variability. Alternative approaches using non-deuterated heavy atom-labeled standards were also explored, though less precise. Notably, no significant isotope effects were observed in product ion formation, validating the reliability of isotopic dilution.
This method provides a comprehensive, high-throughput solution for profiling diverse FA species in complex biological fluids. Its compatibility with standard LC-ESI-MS/MS instrumentation makes it widely accessible. By combining charge reversal derivatization with selective fragmentation, it achieves unprecedented sensitivity and specificity—making it ideal for clinical diagnostics, metabolic phenotyping, and systems biology applications. The ability to detect minor FA species previously undetectable underscores its transformative potential in lipidomic research.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com