Investigation of the Agilent 5977B with High Efficiency Source (HES) to Enable Electron Impact (EI) Analysis of Phenolic Compounds in Water

Significance of the topic

Phenolic compounds pose taste and health concerns in treated water and form chlorinated by-products during disinfection. Sensitive, reliable analysis of these species is critical for environmental monitoring and regulatory compliance.

Objectives and Study Overview

This study aimed to evaluate the Agilent 5977B mass spectrometer with a High Efficiency Source (HES) for electron impact (EI) analysis of 26 phenolic and chlorophenolic compounds in water, replacing a traditional negative chemical ionization (NCI) approach. Automation of liquid-liquid extraction (LLE) and derivatization using pentafluorobenzoyl chloride (PFBCl) was developed to enhance throughput.

Used Instrumentation

• Agilent 7890 GC coupled to 5977B MS with HES
• Gerstel Dual Head MPS 2 autosampler with mVorx agitation
• Anatune CoolRPLUS rapid cooling system
• Gerstel Maestro software for automation

Methodology

A suite of 26 compounds was derivatized with PFBCl and extracted via automated LLE. After acidification, salt addition, and vigorous mixing, the isooctane layer was sampled and injected (2 µL) onto a 30 m × 0.25 mm DB-5MS column. Full-scan and selected ion monitoring (SIM) methods determined optimal ions and compared performance of 5975C, 5977A, and 5977B detectors.

Main Results and Discussion

The 5977B with HES achieved 2–10× higher signal-to-noise ratios versus earlier models. Linearity for most analytes exceeded R² 0.995 down to 50 ng/L, although polychlorinated phenols showed lower responses. Automation using Maestro PrepAhead enabled preparation and analysis of up to 60 samples in 24 hours, doubling throughput vs manual methods.

Benefits and Practical Applications

• Enhanced sensitivity in EI mode without NCI gases
• Seamless method transfer and reduced source switching
• High-throughput automated sample preparation
• Improved reproducibility and reduced labor

Future Trends and Opportunities

Further optimization may include increased injection volumes, alternative derivatization reagents for more specific EI ions, and refining extraction parameters for polychlorinated phenols. Integration with advanced GC-MS techniques could extend applicability to broader environmental matrices.

Conclusion

This investigation demonstrates that the Agilent 5977B HES enables robust EI analysis of phenolic compounds in water, delivering sensitivity and automation benefits that can streamline routine environmental monitoring.