The Use of a Multipurpose Sampler for Headspace GC-MS Analysis of Volatile Organic Compounds in Human Urine and Plasma

Importance of the Topic

The profiling of volatile organic compounds in human urine and plasma offers non-invasive insight into metabolic states and potential exposure to environmental contaminants. Such analyses support disease monitoring, toxicology assessments, and quality control in clinical and industrial laboratories.

Objectives and Study Overview

The primary aim was to evaluate a multi-purpose autosampler for automated headspace GC-MS analysis of volatile organics in acidified human urine and plasma. A pilot clinical comparison of 4-heptanone levels between diabetic patients and healthy controls was also conducted to explore metabolic and environmental origins of this ketone.

Methodology and Instrumentation

Headspace sampling combined controlled heating and vial equilibration with cold-trap enrichment to concentrate volatiles prior to capillary GC-MS detection. Key steps included acidification of samples, vial preheating, gas-tight syringe extraction, and temperature-programmed injection.

• Multi Purpose Sampler (Gerstel MPS) in headspace mode with 1000 µl gas-tight syringe
• HP-7673 tray for 2 ml vials with an additional temperature-controlled preheating module
• Cooled Injection System CIS-3 for analyte focusing and transfer to the column
• Gas chromatograph HP 5890 coupled to MSD HP 5972 (scan range 10–260 amu)
• 60 m × 0.25 mm DB-5 capillary column, helium carrier gas, split/splitless injection

Main Results and Discussion

Calibration for 4-heptanone was linear over 40–800 ng/ml (r = 0.9980) with intra-assay precision CV of 3.0–3.4%. In 92 diabetic patients and 51 controls, median urinary 4-heptanone concentrations were 179 ng/ml and 188 ng/ml, respectively, with broad individual variability. Elevated levels in some healthy individuals and in patients receiving intravenous infusions implicated the plasticizer DEHP as an environmental precursor. Subsequent serum analyses confirmed co-occurrence of 4-heptanone and 2-ethylhexanol in critically ill and hemodialysis patients, supporting in vivo hydrolysis and oxidation of DEHP.

Benefits and Practical Applications

• Automated headspace sampling reduces manual handling and cross-contamination risks.
• Cold trapping enhances sensitivity for low-level volatiles in complex matrices.
• High precision and linearity enable reliable quantitative metabolite profiling.
• Method is adaptable for routine clinical, toxicological, and environmental monitoring.

Future Trends and Opportunities

Further research may focus on distinguishing endogenous metabolic markers from environmental contaminants, expanding the profile of diagnostic volatiles, and integrating chemometric pattern recognition for early disease detection. Development of miniaturized and field-deployable headspace-GC-MS platforms could broaden applications in point-of-care testing and environmental surveillance.

Conclusion

The multi-purpose sampler coupled with cooled injection GC-MS offers a robust and efficient workflow for volatile analysis in human urine and plasma. The method delivers high sensitivity, reproducibility, and throughput, making it a valuable tool for clinical metabolomics and exposure assessment.

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