Increased Reproducibility in the analysis of EU and EPA PAH’s with the Agilent Select PAH GC Column and Metal Microfluidic Guard Chip Technology by Gas Chromatography

Significance of the Topic

The accurate measurement of polycyclic aromatic hydrocarbons (PAHs) at trace levels is critical for environmental monitoring and food safety. EU and EPA regulations demand robust methods to detect 25 PAH compounds plus triphenylene down to low ng/mL concentrations. Complex matrices such as fatty fish oils pose analytical challenges due to matrix buildup in the gas chromatograph, requiring frequent maintenance and risking loss of sensitivity and resolution.

Objectives and Study Overview

This study compares a traditional Agilent 7890 GC system with an Agilent Intuvo 9000 GC featuring a metal microfluidic guard chip and evaluates enhanced matrix removal (EMR-Lipid) sample cleanup. Key goals were:

• Assess resolution and reproducibility of 25 PAH isomers
• Quantify sensitivity loss after repeated injections of salmon oil
• Demonstrate retention time stability after guard chip versus column trims
• Evaluate runtime reduction using a shorter, narrower column
• Test EMR-Lipid cleanup to extend maintenance intervals

Methodology and Instrumentation

Salmon oil was diluted 1:10 in dichloromethane. Standards (1–1 000 ng/mL) were injected every 50 oil injections. Two GC configurations were compared:

• Agilent 7890B GC with Agilent Select PAH column (30 m×0.25 mm×0.15 μm)
• Agilent Intuvo 9000 GC with planar-format Select PAH guard chip and columns (30 m×0.25 mm×0.15 μm and 15 m×0.15 mm×0.10 μm)

GC–MSD conditions were identical (temperature program, carrier gas flow, inlet parameters) and operated in SIM mode. EMR-Lipid cleanup was applied to remove fats.

Findings and Discussion

• Figure 1: Baseline separation of 25 PAH compounds and isomer resolution achieved on both systems.
• Figure 2: Traditional GC lost >50% signal after 50 salmon oil injections; Intuvo with guard chip maintained sensitivity without column trimming.
• Figure 3: Replacement of the Intuvo guard chip produced negligible retention time shifts (<0.01 min), unlike column trims on the 7890.
• Figure 4: Chromatograms from 7890 and Intuvo under identical conditions were virtually indistinguishable in retention and peak height.
• Figure 5: Switching to a 15 m×0.15 mm×0.10 μm column on Intuvo reduced runtime by 15% (54 min vs. 64 min) while preserving resolution, after optimizing flow (0.8 mL/min) and injection volume (0.2 μL).
• Figure 6–7: EMR-Lipid pretreatment of salmon oil prevented lipid buildup, delivering consistent full-scan spectra and stable PAH responses over 50 injections.

Benefits and Practical Applications

• Enhanced reproducibility: Guard chip replacement avoids routine column trims and preserves retention times.
• Reduced maintenance downtime: Easily swapped microfluidic chip versus time-consuming column cutting.
• Improved throughput: Short, narrow columns on Intuvo yield 15% shorter runtimes without lost resolution.
• Extended analysis of fatty samples: EMR-Lipid prep protects inert flow path and maintains signal over prolonged injection sequences.

Future Trends and Opportunities

Integration of microfluidic guard technologies and high-efficiency column formats can be extended to other challenging matrices (e.g., high-fat food, environmental samples). Further miniaturization of GC flow paths and increased adoption of automated lipid cleanup workflows will streamline high-throughput monitoring of regulated contaminants. Advances in source design for low-flow GC–MS promise even greater sensitivity when using narrow-bore columns.

Conclusion

The Agilent Intuvo 9000 GC with metal microfluidic guard chip and EMR-Lipid sample preparation significantly enhances the reproducibility and uptime of PAH analysis in fatty matrices. Transitioning to shorter, narrower columns further improves laboratory efficiency without compromising chromatographic performance. This combined approach addresses both sensitivity and maintenance challenges in routine EU/EPA PAH screening.

Reference

1. K. Lynman. PAH Analysis with High Efficiency GC Columns: Column Selection and Best Practices. Agilent publication 5990-8572EN, 2010.
2. D. Lucas, L. Zhao. PAH Analysis in Salmon with Enhanced Matrix Removal. Agilent publication 5991-6088EN, 2015.
3. J. Oostdijk. Separation of 54 PAHs on an Agilent J&W Select PAH GC Column. Agilent publication SI-02232, 2010.