EPA Method 540: Selected Organic Contaminants Using Agilent Plexa Cartridges and the Agilent 6460 Triple Quadrupole LC/MS

Significance of the Topic

Solid-phase extraction (SPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a cornerstone for monitoring trace organic contaminants in water. USEPA Method 540 standardizes these analyses, but laboratories seek faster, cost-effective workflows that maintain regulatory compliance.

Objectives and Study Overview

This study evaluates Agilent Bond Elut Plexa SPE cartridges combined with the Agilent 1290 Infinity LC and 6460 Triple Quadrupole LC/MS for the analysis of 17 target compounds (12 final method analytes plus five draft-only compounds) under Method 540 guidelines. Key metrics include recoveries, precision, minimum reporting limits, and run time.

Methodology and Instrumentation

Reagents and materials:

• LC/MS-grade water and methanol
• Surrogates: Methomyl-13C2,15N; Tebuconazole-d6
• Internal standards: Carbofuran-13C6, Bensulide-d14, Phorate-d10
• Agilent Bond Elut Plexa SPE cartridge (200 mg, 6 mL)
• Agilent Poroshell 120 Phenyl-Hexyl column (3.0 × 100 mm, 2.7 µm)

Sample preparation:

• Preserve 250 mL water samples per EPA protocol, fortify with surrogates
• Condition SPE with methanol and reagent water, load sample, rinse, and elute with methanol in two steps
• Concentrate extract to ~1 mL, add internal standards, adjust to ~1.7 mL final volume

Chromatography and MS conditions:

• LC gradient run time: 18 min (40 °C, 0.4–0.6 mL/min)
• MS detection: Agilent 6460 Triple Quadrupole, positive ESI dynamic MRM

Main Results and Discussion

Recovery and precision:

• Recoveries ranged from 65 % to 116 %, with two analytes marginally below the 70 % threshold; all %RSD values were 2.6 %–12 %, well under the 20 % limit.
• Plexa SPE performance matched or exceeded the Oasis HLB benchmark, even for draft-only compounds.

Limit of quantitation (LCMRL):

• Calculated LCMRLs were at or below EPA requirements for 14 analytes (1.7–63× lower).
• Three analytes showed LCMRLs up to 2.5× higher than EPA draft values but remained fit-for-purpose.

Throughput:

• Analysis time was reduced to 18 min per injection versus 40 min in Method 540, effectively doubling sample throughput.

Benefits and Practical Applications

This workflow delivers regulatory-compliant quantitation of pesticides and metabolites at lower reporting limits and higher throughput. It streamlines SPE handling, reduces solvent consumption, and extends column lifetime, making it attractive for environmental and industrial laboratories.

Future Trends and Opportunities

Emerging directions include micro-SPE formats, ultrafast UHPLC separations, and machine-learning-driven optimization of MRM methods. Integration with automated sample preparation and data processing will further enhance large-scale water monitoring capabilities.

Conclusion

The Agilent Plexa SPE combined with the 1290 Infinity LC and 6460 Triple Quadrupole LC/MS meets and often exceeds EPA Method 540 performance criteria, delivering faster, more sensitive, and cost-effective analysis for laboratories seeking flexible compliance solutions.

Reference

1. Determination of Selected Organic Chemicals in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS), USEPA Method 540.
2. Winslow SD, et al. Statistical procedures for determination and verification of minimum reporting levels for drinking water methods. Environ Sci Technol. 2006;40:281–288.