Method for Direct Analysis of Contaminants in Surface Waters With High Accuracy and Precision Using an Agilent 6470A Triple Quadrupole LC/MS System

Importance of the Topic

Contamination of surface waters by pharmaceuticals, personal care products (PPCPs) and related agrochemicals at trace (ng/L) levels poses a growing threat to ecosystems and human health. Conventional monitoring methods rely heavily on solid‐phase extraction and extensive sample cleanup, which are time‐consuming and prone to matrix effects. A direct injection LC/MS/MS approach that achieves low detection limits, wide dynamic range, and high precision can streamline environmental surveillance and regulatory compliance.

Objectives and Study Overview

This study aimed to develop and validate a direct‐injection method for quantitative analysis of 28 priority surface‐water contaminants—including PPCPs, sucralose, herbicides (2,4‐D, atrazine, diuron), and insecticides (diazinon, DEET)—using an Agilent 1290 Infinity II UHPLC coupled to an Agilent 6470A Triple Quadrupole LC/MS system. Key goals included assessing sensitivity (LLOQs, IDLs), linearity, precision, accuracy, and demonstrating minimal sample preparation requirements.

Methodology and Instrumentation

A set of 28 standard compounds was spiked into ultrapure water at 16 concentration levels (0.1–5000 ng/L). Environmental samples were collected from Colorado’s Poudre and Big Thompson Rivers, filtered (0.22 µm), and aliquoted for analysis. Direct injection of 40 µL filtered water was performed without prior SPE. Chromatographic separation used an Agilent ZORBAX Eclipse Plus RRHD C18 column (2.1×50 mm, 35 °C) with a 0.4 mL/min gradient (0.03% formic acid in water vs acetonitrile). MS detection employed multiple-reaction monitoring (MRM) in positive and negative ion modes, with optimized fragmentor voltages, collision energies, and resolution settings.

Instrumentation

• Agilent 1290 Infinity II UHPLC system
• Agilent 6470A Triple Quadrupole LC/MS with Jet Stream (AJS) ion source
• Agilent ZORBAX Eclipse Plus RRHD C18 column (2.1×50 mm)
• Milli-Q ultrapure water system

Key Findings and Discussion

The method achieved limits of quantitation from 0.1 to 50 ng/L and instrument detection limits (IDLs) as low as 0.012 ng/L for select analytes. Calibration curves exhibited excellent linearity (R2 > 0.995) over four orders of magnitude. Precision at the LLOQ was under 20% RSD and below 15% at higher levels; accuracy ranged 80–120% at the LLOQ and 85–115% at other points. The Agilent 6470A system outperformed its predecessor (6460) by reducing area‐response variability at low concentrations. Direct injection of environmental water yielded comparable sensitivity to SPE-enriched samples, simplifying the analytical workflow.

Benefits and Practical Applications

• Sub-ng/L sensitivity for diverse contaminants without extensive sample enrichment
• Reduced solvent consumption and hands-on time
• High throughput analysis suitable for routine water quality monitoring
• Robust quantitation meeting EPA Method 1694 validation criteria

Future Trends and Applications

Advances in triple quadrupole LC/MS technology will further lower detection limits and expand the list of target analytes. Integration with automated sample handling and high-resolution mass spectrometry holds promise for non-target screening of emerging contaminants. The streamlined direct-injection approach can be adopted by regulatory laboratories to enhance surveillance of surface waters and support risk assessment frameworks.

Conclusion

This application demonstrates that direct injection on an Agilent 6470A Triple Quadrupole LC/MS system provides a rapid, accurate, and precise method for quantifying trace contaminants in surface water. The approach minimizes sample preparation, achieves low-ng/L quantitation, and meets stringent validation requirements, facilitating efficient environmental monitoring.

References

1. U.S. EPA. Pharmaceuticals and Personal Care Products in Water. 2015.
2. U.S. EPA Method 1694: HPLC/MS/MS for PPCPs in Environmental Samples. 2007.
3. Directive 2013/39/EU: Priority Substances in Water Policy. Official Journal of the EU, 2013.
4. Directive 2008/105/EC: Environmental Quality Standards in Water. Official Journal of the EU, 2008.
5. Decision 2455/2001/EC: List of Priority Substances in Water Policy. Official Journal of the EU, 2001.
6. Commission Directive 2009/90/EC: Technical Specs for Chemical Analysis of Water. Official Journal of the EU, 2009.
7. Wiklund AK et al. Sucralose—An ecotoxicological challenger? Chemosphere, 86:50–55, 2012.
8. Daughton CG. Pharmaceuticals as Environmental Pollutants. Int. Encyclopedia of Public Health, 5:66–102, 2008.
9. Goodman LS, Gilman A. The Pharmacological Basis of Therapeutics, 9th Ed., McGraw-Hill, 1996.