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

Importance of the Topic

Nonylphenol is a known endocrine disrupting compound frequently detected in aquatic environments. Reliable identification and quantitation of its thirteen isomeric forms are critical for environmental monitoring and regulatory compliance. Traditional GC MS methods often struggle with low sensitivity for minor isomers and suffer from interference by river water matrices.

Objectives and Study Overview

The study aimed to develop a high-sensitivity analytical workflow for nonylphenol isomer profiling in river water using triple quadrupole GC MS MS. Key goals included optimizing chromatographic separation of all thirteen 4-nonylphenol isomers, enhancing detection limits for low abundance isomers, and simplifying sample pretreatment by omitting cleanup steps that reduce recovery.

Methodology and Instrumentation

The analytical approach combined high-pressure solid phase extraction with GC MS MS in multiple reaction monitoring mode. Major steps and components included:

• Sample Pretreatment: 500 mL river water passed through an Oasis HLB Plus cartridge under 200 kPa using an AQUALoader Twin device. Elution solvent was evaporated and reconstituted without silica cleanup.
• GC MS/MS System: Shimadzu GCMS TQ8040 with Rxi-5ms column (30 m x 0.25 mm, 0.25 µm film). Ion source 230 C, interface 280 C, injection port 250 C, splitless injection of 2 µL.
• GC Conditions: Constant linear velocity 40 cm/s; oven program 50 C hold 1 min, ramp 8 C/min to 300 C, hold 3 min.
• Mass Spectrometry: Q3 SIM mode for single quadrupole GC MS comparisons; optimized MRM transitions for each isomer in GC MS MS with 0.3 s event time.
• Calibration Standards: Thirteen nonylphenol isomers, surrogate 13C6 labeled standard, and d4 internal standard at concentrations 0.01 to 0.5 µg/mL.

Main Results and Discussion

Chromatographic separation of all thirteen 4-nonylphenol isomers was achieved on the Rxi-5ms column at 40 cm/s. In Q3 SIM mode, the twelfth isomer was near the detection limit (S/N 5.6). MRM optimization yielded a 50-fold sensitivity improvement for this minor isomer without additional cleanup. Calibration curves for all isomers were linear (R > 0.9999) and repeatability remained below 7.5% RSD. In spiked river water samples, MRM mode effectively eliminated matrix interferences that compromised identification in SIM mode.

Benefits and Practical Applications

The optimized GC MS MS workflow delivers:

• Enhanced sensitivity for low composition isomers, enabling accurate trace quantitation.
• Isomer specific profiling critical for environmental risk assessment.
• Simplified pretreatment by eliminating post-elution cleanup while maintaining acceptable recoveries (50 to 120%).
• Robust performance in complex matrices such as river water.

Future Trends and Applications

Potential expansions include application to other trace organic pollutants requiring isomer separation, integration with high resolution mass spectrometry for unknown screening, and portable GC MS MS platforms for field analysis. Advances in sample preparation, such as automated microextraction techniques, may further streamline workflows.

Conclusion

The study demonstrates that targeted MRM on a triple quadrupole GC MS MS system significantly improves detection and quantitation of nonylphenol isomers in river water. The approach achieves full isomer resolution, excellent linearity, and strong repeatability without complex cleanup, offering a reliable tool for environmental monitoring of endocrine disruptors.

Reference

No external literature references provided.