Trace level determination of Polycyclic Aromatic Hydrocarbons in blood plasma using GC-MS/MS

Significance of the Topic

Polycyclic aromatic hydrocarbons (PAHs) are potent environmental carcinogens and toxicants that accumulate in human tissues following inhalation, ingestion or dermal exposure. Their presence in blood plasma reflects recent exposure and internal dose, making sensitive quantification in this complex matrix critical for epidemiological studies, clinical investigations and regulatory monitoring.

Objectives and Study Overview

This work aims to develop and partially validate a single, streamlined GC-MS/MS method for trace-level determination of 16 priority PAHs in human blood plasma. The study encompasses sample extraction, cleanup, chromatographic separation, mass spectrometric detection and evaluation of key performance parameters (linearity, limit of quantitation, precision and recovery).

Methodology and Instrumentation

• Sample Preparation: A 1 mL plasma aliquot was extracted twice with 2 mL of n-hexane/acetone (1:1) by vortex mixing and centrifugation. The combined organic phases underwent solid-phase cleanup using florisil and anhydrous ammonium sulfate, then dried under nitrogen and reconstituted in 500 µL of acetone/hexane (1:1).
• Chromatography and Detection: An optimized GC-MS/MS method employing multiple reaction monitoring (MRM) transitions for all 16 PAHs enabled high selectivity and sensitivity. Calibration spanned 5–100 ppb in matrix-matched standards.

Instrumental Setup

• GC-MS/MS System: Shimadzu GCMS-TQ8040 NX with AOC-20i + s auto-injector.
• Column: SH-I-PAH, 60 m × 0.25 mm ID, 0.10 μm film thickness.
• Injector: Splitless mode at 320 °C, injection volume 1 µL.
• Oven Program: 60 °C (1 min), ramp to 160 °C at 35 °C/min, to 260 °C at 3.5 °C/min, then to 350 °C at 15 °C/min (total run time 53.5 min).
• Carrier Gas: Helium at constant linear velocity (31.6 cm/s).
• Ion Source: Electron ionization, interface 320 °C, source 230 °C.
• MRM Transitions: Two transitions per analyte optimized for target and reference ions.

Results and Discussion

Calibration curves in plasma exhibited excellent linearity (r2 > 0.99) over 5–100 ppb. The limit of quantitation was established at 5 ppb for all PAHs based on S/N ≥ 10. Precision (repeatability) at LOQ showed %RSD below 15% for six replicates. Recovery studies yielded 70–120% recovery for pre- and post-spiked samples with %RSD also under 15%, demonstrating reliable quantitation in a challenging matrix.

Practical Benefits and Applications

This method offers a rapid, sensitive and robust approach for monitoring human exposure to PAHs via plasma analysis. It supports biomonitoring in occupational and environmental health studies, clinical toxicology, and QA/QC in research laboratories with minimal sample volume and straightforward cleanup.

Future Trends and Applications

• Automation of extraction and cleanup to increase throughput.
• Integration with high-resolution mass spectrometry for non-target screening of emerging PAH derivatives.
• Application to other biological matrices (urine, tissues) and validation under regulatory guidelines.
• Expansion to include phase II metabolites or isotopically labeled internal standards for improved quantitation.

Conclusion

A single GC-MS/MS method was successfully developed and partially validated for trace-level quantitation of 16 PAHs in human plasma. The approach demonstrated satisfactory sensitivity, precision and accuracy, making it suitable for routine biomonitoring and exposure assessment.

Reference

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