High Sensitivity GC/MS/MS Analysis of Nonpolar Organic Compounds in Water Using the Agilent 7000 Triple Quadrupole GC/MS

Importance of the Topic

Ensuring reliable detection of nonpolar organic contaminants in water is critical for protecting public health and the environment. Methods capable of low detection limits and confident compound identification support regulatory compliance and inform water treatment strategies.

Objectives and Study Overview

The study describes development and validation of a high-sensitivity gas chromatography tandem mass spectrometry (GC/MS/MS) method on the Agilent 7000 Triple Quadrupole GC/MS.
The goals were to achieve:

• Detection of 51 nonpolar organic compounds (pesticides, PCBs) in potable water at ng/L levels
• Detection of PBDEs, PAHs, and diazinon in wastewater at sub-ng/L levels
• Short run times (<20 min) and robust, straightforward sample preparation

Methodology and Instrumentation

Sample preparation for potable water involved a simple liquid extraction with minimal modification from earlier GC/ECD protocols. Wastewater required more extensive concentration steps to reach sub-ng/L reporting limits.

• Gas chromatograph: Agilent 7890 Series GC with multimode inlet and cryogenic cooling
• Mass spectrometer: Agilent 7000 Triple Quadrupole in multiple reaction monitoring (MRM) mode
• Column: DB-1 nonpolar stationary phase, single column for all 51 analytes
• Data analysis: Agilent MassHunter software

Key Results and Discussion

The method demonstrated:

• Limits of detection (LODs) ≤2 ng/L for most potable water analytes (captan 3 ng/L)
• Method reporting limits (MRLs) <0.2 ng/L for selected compounds in wastewater
• Recoveries between 98.4% and 105.1% at prescribed concentration values (0.1 µg/L) with RSDs ≤7.4%
• Calibration linearity (R²>0.998) over 10–120 ng/L
• Chromatographic separation of DDT and HCH isomers within a 12-minute run time
• Robust detection of cypermethrin at 2.5 ng/L and PBDE 47 at 1 ng/L in crude sewage
• Wide dynamic range illustrated by diazinon quantification from 0.7 ng/L in landfill leachate to 1,300 ng/L in industrial effluent

Benefits and Practical Applications

The GC/MS/MS approach offers:

• Enhanced selectivity and structural confirmation versus traditional GC/ECD
• Reduced analysis time by using a single column and large injection volumes
• High sensitivity in clean and complex matrices
• UKAS accreditation for potable water testing in routine laboratory operation

Future Trends and Potential Applications

Potential developments include:

• Expansion to emerging organic contaminants and transformation products
• Automated sample preparation workflows to increase throughput
• Integration with advanced data analytics and laboratory information management systems
• Adaptation to evolving regulatory requirements and environmental monitoring programs

Conclusion

The Agilent 7000 Triple Quadrupole GC/MS method provides a rapid, robust, and highly sensitive platform for nonpolar organic compound analysis in potable and wastewater matrices. Its low detection limits, strong precision, and accreditation support routine environmental monitoring and regulatory compliance.