Screening of organic acids for nutritional and metabolic profiling from dried urine spots using Gas Chromatograph Mass Spectrometer

Significance of the topic

Urinary organic acids are key intermediates in metabolic pathways and serve as indicators of bacterial metabolism, nutrient status and microbiome health. Screening these acids provides insights into energy metabolism, hormone function and gut health, aiding in the detection of nutritional deficiencies and metabolic disorders.

Objectives and study overview

This study presents a proof-of-concept workflow for comprehensive profiling of organic acids from dried urine spots. The aim was to develop a rapid, robust GC-MS method that can qualitatively screen a broad spectrum of metabolites for nutritional and metabolic profiling.

Methodology and instrumentation

Sample preparation involved collecting dried urine on filter paper, adjusting sample volume based on creatinine, adding internal standards (margaric acid and C24), enzymatic urea degradation, deproteinization with ethanol, and trimethylsilyl derivatization. Analysis was performed in Scan mode on a Shimadzu GCMS-QP2020 NX system equipped with an AOC-20i+s autosampler, using a SH-Rxi-5Sil MS capillary column (30 m × 0.25 mm × 0.25 µm) and a Restek Topaz™ liner. The GC oven ramped from 60 °C to 310 °C, with a total run time of 23.7 min.

Main results and discussion

Utilizing the Smart Metabolite Database Ver. 2 and Automatic Adjustment of Retention Time (AART), the method enabled reliable matching of mass spectra and predicted retention indices. A total of 65 organic acids, including lactic, glycolic, phosphoric and fatty acids, were screened. Representative chromatograms demonstrated clear separation and detection of target compounds. Elevated levels of specific acids correlated with conditions such as systemic lupus erythematosus, highlighting the clinical relevance of rapid screening.

Benefits and practical applications of the method

The workflow offers fast, accurate qualitative screening from minimal sample volumes on dried urine spots. It supports nutritional assessment, metabolic profiling, early biomarker discovery and monitoring of chronic conditions in clinical, research and QA/QC laboratories.

Used instrumentation

• Shimadzu GCMS-QP2020 NX system
• AOC-20i+s autosampler
• SH-Rxi-5Sil MS capillary column (30 m, 0.25 mm, 0.25 µm)
• Restek Topaz™ liner with wool

Future trends and potential applications

Advances may include expanded metabolite libraries, integration with high-resolution MS, enhanced automation and data analysis, and multi-omics approaches for personalized nutrition, disease monitoring and preventive healthcare.

Conclusion

The developed GC-MS method enables efficient qualitative screening of a wide range of organic acids from dried urine spots. Leveraging AART and a comprehensive database ensures rapid, precise identification, facilitating metabolic and nutritional profiling in various applications.

References

• Lord RS, Bralley JA. Clinical applications of urinary organic acids. Part 2. Dysbiosis markers. Altern Med Rev. 2008;13(4):292-306.
• Yan R, Jiang H, Gu S, Feng N, Zhang N, Lv L, Liu F. Fecal metabolites altered in systemic lupus erythematosus in a GC-MS-based metabolomics study. Front Immunol. 2020;11:2138.
• Chen YY, Chen DQ, Chen L, Liu JR, Vaziri ND, Guo Y, Zhao YY. Microbiome–metabolome reveals the contribution of gut–kidney axis on kidney disease. J Transl Med. 2019;17:1-11.