Integrating Electrostatic Adsorption-Laser Desorption/Ionization-MS with a Derivative Full-Spectrum Internal Standard Approach for Acylcarnitine Quantification in Clinical Samples

Acylcarnitines (ACs), essential intermediates in fatty acid β-oxidation, are increasingly recognized as biomarkers for inborn errors of metabolism (IEM), insulin resistance, heart failure, and neurodegenerative diseases. However, conventional liquid chromatography–mass spectrometry (LC-MS) and flow injection–mass spectrometry (FI-MS) methods are hindered by complex sample preparation, limited throughput, and matrix interferences. Meanwhile, matrix-assisted laser desorption/ionization–MS (MALDI-MS) suffers from low-mass background noise and poor reproducibility. Here, we present a dual-innovation mass spectrometry platform combining a substrate composed of sulfonic acid–gold nanoparticle-decorated silicon nanowires (Sulfo-Au-SiNWs) for electrostatic adsorption-laser desorption/ionization (EALDI) and a full-spectrum internal standard (FS IS) strategy based on d6-ethanol derivatization. The optimized Sulfo-Au-SiNWs offer uniform crystallinity, in situ electrostatic enrichment, efficient thermal desorption, and gold-mediated charge–hole separation, resulting in a ∼300% increase in AC signal intensity. This enabled the selective detection of over ten medium- and long-chain ACs that were previously undetectable using unmodified SiNWs. The FS IS method incorporates over 30 derivatized AC species, enabling simultaneous quantification with detection limits below 0.01 μmol/L, surpassing the sensitivity of traditional FI-MS. The platform delivers spike recovery rates of 96–112% and supports high-throughput analysis, processing each sample within seconds. Validation against FI-ESI-MS/MS in both urine and dried blood spot samples demonstrated excellent agreement (ρ > 0.95) and effectively identified IEM patient profiles via statistically significant AC elevations. With strong intra- and interbatch precision (median RSD < 12.5%) and substrate stability exceeding one month, this EALDI-MS/FS IS workflow provides a high-throughput, high-coverage, and quantitatively robust solution for clinical AC profiling and newborn screening.