EPA Method 543: Selected Organic Contaminants by Online SPE LC/MS/MS Using the Agilent Flexible Cube

Significance of the topic

Monitoring trace organic contaminants in drinking water is essential for protecting public health and meeting regulatory requirements. Online solid‐phase extraction (SPE) coupled with LC/MS/MS offers a streamlined approach that minimizes sample volumes, reduces solvent use, lowers labor costs, and accelerates turnaround compared to conventional offline SPE.

Study objectives and overview

This application note evaluates the use of Agilent Flexible Cube online SPE in conjunction with EPA Method 543 to analyze seven targeted organic compounds in water. Key objectives include demonstrating method performance, reducing overall run time, and achieving comparable accuracy, precision, and sensitivity.

Methodology and instrumentation

• Online SPE setup: Agilent 1290 Infinity Flexible Cube module with a single‐piston pump, three‐solvent selector valve, and two 10‐port/2‐position valves for alternating trap cartridges.
• SPE cartridges: Agilent PLRP‐S cartridges capture analytes from 1.8 mL injections (equivalent to processing 360 mL offline in terms of analyte load).
• Chromatography: Agilent 1200 Infinity Series with Poroshell 120 Phenyl‐Hexyl column (3.0 × 100 mm, 2.7 µm), gradient elution at 0.4–0.6 mL/min, total cycle time 18 min.
• Mass spectrometry: Agilent 6460A Triple Quadrupole with Jet Stream ESI in positive mode, dynamic multiple reaction monitoring (dMRM) transitions for seven analytes and three labeled internal standards.

Results and discussion

• Chromatography: Baseline resolution and sharp, symmetric peaks achieved after backflush from SPE onto the analytical column.
• Speed: Total runtime reduced to 18 minutes from the 28–40 minutes reported in the original Method 543.
• Calibration: Quadratic fits with 1/x weighting yielded correlation coefficients (R²) > 0.999 across ng/L concentration ranges.
• Accuracy: Recoveries ranged from 87 % to 107 % in reagent water and from 93 % to 104 % in surface water, in line with EPA benchmarks.
• Precision: RSD values were generally below 5 % in reagent water and below 7 % in surface water, matching or exceeding Method 543 criteria.
• Sensitivity: Calculated lowest concentration minimum reporting levels (LCMRLs) were mostly lower than EPA values, demonstrating enhanced method sensitivity.

Benefits and practical applications

• Automated online SPE reduces sample handling, solvent consumption, and manual labor.
• Integrated valving and pump system lowers complexity and cost compared to multi‐pump configurations.
• Alternating trap cartridges support high sample throughput and continuous operation.
• Full compliance with EPA Method 543 for routine monitoring of organic contaminants in drinking water.

Future trends and possibilities

Future developments may include expanded compound panels for emerging contaminants, real‐time data processing with advanced analytics, portable field‐deployable SPE‐MS systems, and further automation to support high‐volume water testing laboratories.

Conclusion

The Agilent Flexible Cube online SPE module combined with LC/MS/MS implements EPA Method 543 with half the run time while maintaining or improving accuracy, precision, and sensitivity. This streamlined workflow provides a robust, high‐throughput solution for regulatory and research laboratories analyzing trace organic contaminants in water.

References

• Draft EPA Method 543 – Determination of Selected Organic Chemicals in Drinking Water by On‐Line Solid Phase Extraction and LC/MS/MS; EPA/600/R‐14/098, March 2015.
• Mohsin SB, Woodman M. Quantitation of Trace Level Emerging Contaminants in Water Using Online SPE with LC/MS/MS. Agilent Technologies Application Note 5991-2731EN, 2013.
• Schuhn B, Naegle E, Glauner T. Detection of Trace-Level Herbicides in Drinking, Surface, and Ground Water Using the Agilent Infinity Series Online SPE Solution. Agilent Technologies Application Note 5991-2405EN, 2013.
• Winslow SD et al. Statistical procedures for determination and verification of minimum reporting levels for drinking water methods. Environ. Sci. Technol. 40, 281–288 (2006).