DeArmond PD, Bunch DR. Quantitation of non-derivatized free amino acids for detecting inborn errors of metabolism by incorporating mixed-mode chromatography with tandem mass spectrometry.
J Mass Spectrom Adv Clin Lab 2022;
25:1-11. [PMID:
35637738 PMCID:
PMC9142622 DOI:
10.1016/j.jmsacl.2022.05.002]
[Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 05/09/2022] [Accepted: 05/19/2022] [Indexed: 11/18/2022] Open
Abstract
Analysis of 39 free amino acids in 15 min LC-MS/MS run.
Validation of method in both plasma and urine.
Chromatographically resolves leucine, isoleucine, and allo-isoleucine.
Introduction
Amino acids are critical biomarkers for many inborn errors of metabolism, but amino acid analysis is challenging due to the range of chemical properties inherent in these small molecules. Techniques are available for amino acid analysis, but they can suffer from long run times, laborious derivatization, and/or poor resolution of isobaric compounds.
Objective
To develop and validate a method for the quantitation of a non-derivatized free amino acid profile in both plasma and urine samples using mixed-mode chromatography and tandem mass spectrometry.
Methods
Chromatographic conditions were optimized to separate leucine, isoleucine, and allo-isoleucine and maintain analytical runtime at less than 15 min. Sample preparation included a quick protein precipitation followed by LC-MS/MS analysis. Matrix effects, interferences, linearity, carryover, acceptable dilution limits, precision, accuracy, and stability were evaluated in both plasma and urine specimen types.
Results
A total of 38 amino acids and related compounds were successfully quantitated with this method. In addition, argininosuccinic acid was qualitatively analyzed. A full clinical validation was performed that included method comparison to a reference laboratory for plasma and urine with Deming regression slopes ranging from 0.38 to 1.26.
Conclusion
This method represents an alternative to derivatization-based methods, especially in urine samples where interference from metabolites and medications is prevalent.
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