The Use of a Multi Purpose Sampler for Headspace GC-MS Analysis of Volatile Organic Compounds in Human Urine

Significance of the Topic

Volatile organic compounds (VOCs) in human urine provide a non-invasive window into metabolic status and disease processes. Profiling these compounds supports early detection and monitoring of disorders such as diabetes mellitus, hepatic dysfunction and infectious diseases.

Objectives and Study Overview

The study evaluated the suitability of a versatile automated sampler for headspace GC-MS analysis of urinary VOCs. Key aims included:

• Assessing sensitivity and reproducibility for ketone and glucose positive samples versus healthy controls
• Comparing VOC profiles with and without urine acidification
• Demonstrating automation and cost-efficiency in a routine clinical setting

Methodology and Instrumentation

Sample Preparation:

• Standard 2 mL GC vials containing 1 mL of human urine, some acidified (pH adjustment) and others untreated

Headspace Sampling and GC-MS Conditions:

• Multi Purpose Sampler (Gerstel MPS) in headspace mode with 1000 µL gas-tight syringe
• Pre-heating module (70 °C, 10 min), syringe and turret at 70 °C
• Cold Injection System (CIS-3) cooled to 10 °C, heated to 300 °C at 12 °C/s for analyte focusing
• Capillary GC column DB-5 (60 m × 0.25 mm, 0.25 µm film), helium carrier gas (100 kPa), split and splitless injection
• Oven program: 60 °C to 100 °C at 5 °C/min, then to 240 °C at 25 °C/min
• Mass spectrometer (HP 5972 MSD), scan range 10–260 amu, transfer line 280 °C

Main Results and Discussion

Acidification markedly increased the number and intensity of detected peaks. Identified VOCs included acetone, 2-butanone, 2-pentanone, 4-heptanone, various sulfur compounds and aldehydes. Key observations:

• Acidified samples exhibited richer chromatographic patterns than non-acidified ones
• Distinct ketone profiles correlated with health status: elevated 4-heptanone in diabetic and renal-failure samples
• Reproducibility for 4-heptanone area counts showed relative standard deviations of 3.0–4.9 %

Benefits and Practical Applications

The automated headspace GC-MS workflow offers:

• High throughput with a 100-vial tray and dedicated pre-heating module
• Enhanced sensitivity via cold trapping and splitless injection
• Robust reproducibility suitable for routine clinical analysis
• Cost efficiency through versatile sampler reuse across sample types

Future Trends and Applications

Ongoing and future developments may include optimization of sample volume, pH adjustment, salt addition and multiple headspace extraction to improve sensitivity. Integration of pattern-recognition algorithms and expansion to other biofluids could further enhance diagnostic capabilities. Coupling with selective detectors for sulfur, nitrogen or halogen species may deepen metabolic insights.

Conclusion

The Gerstel Multi Purpose Sampler combined with headspace GC-MS provides a sensitive, reproducible and highly automated platform for urinary VOC profiling. Preliminary results demonstrate its potential for routine clinical use, with further optimization planned to refine operating conditions and analytical performance.

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