High-Sensitivity Analysis of Nonylphenol in River Water Using GC-MS/MS

Significance of the Topic

Nonylphenol is a widespread alkylphenol used in surfactant manufacture and as an antioxidant for plastics and rubber. Recognized as an endocrine-disrupting compound, its branched isomers persist in aquatic environments and pose ecological and health risks. Accurate, sensitive detection of individual isomers in complex water matrices is essential for environmental monitoring and regulatory compliance.

Objectives and Study Overview

This study aimed to develop and validate a high-sensitivity method for isomer-specific quantitation of thirteen 4-nonylphenol isomers in river water. By adopting triple-quadrupole GC-MS/MS and optimizing multiple reaction monitoring conditions, the goal was to overcome limitations of conventional GC-MS, particularly for low-abundance isomers, and to simplify sample preparation without sacrificing accuracy.

Methodology

River water samples (500 mL) underwent solid-phase extraction using Oasis HLB cartridges with high-pressure loading. Eluates were dried, reconstituted, and analyzed by GC-MS/MS. Calibration solutions spanning 0.01 to 0.5 µg/mL were prepared with a 13C6 surrogate and d4 internal standard at 0.1 µg/mL.

Instrumentation Used

Triple-quadrupole GC-MS/MS system GCMS-TQ8040
Column Rxi-5ms, 30 m×0.25 mm I.D., 0.25 µm film thickness
Injection splitless, 2 µL; carrier gas linear velocity 40 cm/s
Oven program 50 °C (1 min) to 300 °C at 8 °C/min, hold 3 min
Ion source 230 °C, interface 280 °C
Acquisition modes SIM (GC-MS) and MRM (GC-MS/MS)

Main Results and Discussion

All thirteen 4-NP isomers were baseline-separated under optimized conditions. In GC-MS/MS MRM mode, the lowest-ratio isomer (NP12) exhibited a 50-fold sensitivity gain compared to SIM, enabling reliable detection at 0.01 µg/mL. Calibration curves for each isomer showed excellent linearity (R≥0.9999), and repeatability RSD values were below 6 % for most isomers. In spiked river water, surrogate recoveries ranged from 64 to 77 %. MRM effectively suppressed matrix interferences, allowing clear peak identification without a laborious cleanup step.

Benefits and Practical Applications

• Selective and sensitive quantitation of NP isomers in environmental samples
• Reduced sample preparation time by omitting post-elution cleanup
• High throughput monitoring for regulatory and QA/QC laboratories
• Improved confidence in low-level contaminant detection and risk assessment

Future Trends and Potential Applications

Advances may include automated on-line SPE coupling, miniaturized GC-MS/MS systems for field deployment, and integration with high-resolution mass analyzers for nonylphenol metabolites. Data analytics and digital reporting will enhance real-time monitoring of endocrine disruptors in diverse water bodies.

Conclusion

Optimized GC-MS/MS in MRM mode provides a robust and highly sensitive approach for isomer-specific analysis of nonylphenol in river water. With streamlined sample preparation and superior matrix tolerance, this workflow supports environmental surveillance and regulatory compliance.

References

No additional literature cited.