Comparison of Online SPE Analysis and Direct Injection of Trace Level Estrogens in Drinking Water with the Agilent 6460 and Agilent 6490 Triple Quadrupole LC/MS Systems

Significance of the Topic

The occurrence of natural and synthetic estrogens in drinking water poses ecological and human health concerns due to their endocrine-disrupting potential. Regulatory directives demand analytical methods capable of quantifying trace hormone levels at sub-nanogram per liter concentrations. High sensitivity and robust throughput are critical for routine environmental monitoring and compliance.

Objectives and Study Overview

This work compares direct injection and online solid-phase extraction (SPE) coupled with triple quadrupole LC/MS for trace estrogen analysis in drinking water. Performance metrics—sensitivity, linearity, reproducibility, and carryover—were evaluated on Agilent 6460 and 6490 QqQ systems integrated with the Agilent 1200 Infinity Series online SPE solution.

Methodology and Instrumentation

• Instrumental Setup:
  • Agilent 1200 Infinity Series online SPE solution with 1290 Infinity Flexible Cube and 5 mL high-volume injection loop
  • Agilent 6460 and 6490 triple quadrupole LC/MS with Jet Stream and iFunnel technology
  • Agilent 1260 Infinity binary pump and 1290 Infinity thermostatted column compartment
  • SPE cartridges: Agilent ZORBAX Eclipse Plus C18 guard cartridges
  • Analytical column: Agilent Poroshell 120 Phenyl-Hexyl
• Sample Preparation: Direct injection (250 µL) versus online SPE (4.5 mL) of spiked tap water
• Mobile Phase: Water with 1 mM ammonium fluoride (A) and methanol-acetonitrile (65:35) (B)
• MRM Parameters: Two transitions per estrogen optimized for negative electrospray ionization
• Calibration: Seven-level curves ranging from low-ng/L to sub-ng/L

Main Results and Discussion

• Linearity: R² ≥ 0.997 across all estrogens and methods
• Sensitivity Gain: Online SPE improved detection limits by 2–10× versus direct injection
• Limits of Detection: As low as 0.02 ng/L for estrone and hexoestrol on the 6490 system with online SPE
• Limits of Quantification: Down to 0.05 ng/L for key analytes
• Precision: Peak area RSD < 15 %; retention time RSD ~0.1 %
• Carryover: Negligible, with only 1 % observed for 17α-ethinylestradiol on the 6460 system

Benefits and Practical Applications

The integrated online SPE approach streamlines sample cleanup and chromatographic separation within a single HPLC module, reducing manual steps and increasing throughput. Laboratories can achieve sub-ng/L sensitivity on a routine 6460 system or ultra-trace detection on a high-end 6490 system, supporting stringent environmental compliance and quality assurance.

Future Trends and Opportunities

• Development of novel SPE materials and chemistries for broader contaminant classes
• Integration of high-resolution MS for non-targeted screening
• Automation of sample loading, data acquisition, and processing to enhance throughput
• Application expansion to emerging pollutants in complex matrices
• Standardization of workflows for regulatory and QA/QC laboratories

Conclusion

Online SPE coupled with triple quadrupole LC/MS offers significant sensitivity and precision improvements for estrogen analysis in drinking water. The Agilent 1200 Infinity Series solution, especially when paired with the 6490 QqQ system, achieves detection limits in the tens of picograms per liter, fulfilling regulatory requirements while maintaining high throughput and robustness.

References

• López de Alda M.J. and Barceló D. Use of solid-phase extraction in various modalities for determination of estrogens and progesterones in sediment and water. J. Chromatogr. A 938, 145–153 (2001).
• Ronan J.M. and McHugh B. Sensitive LC-MS/MS method for natural and synthetic steroid estrogens in seawater and biota focusing on WFD standards. Rapid Commun. Mass Spectrom. 27, 738–746 (2013).
• Directive 2000/60/EC establishing a framework for Community action in water policy. Official Journal of the European Communities (2000).
• Schuhn B. High volume injection up to 5 mL with the Agilent 1200 Infinity Series Online SPE Solution for highest sensitivity. Tech. Overview 5991-3173EN (2013).
• Naegele E. Comparison of Direct Injection and Online SPE for quantification by LC/MS of trace-level herbicides in water. App. Note 5991-2140EN (2013).
• Hindle R. Improved analysis of trace hormones in drinking water by LC/MS/MS (EPA 539) using the Agilent 6460 QqQ. App. Note 5991-2473EN (2013).