Reduction of Matrix Effects with the Agilent 1200 Infinity Series Online SPE Solution

Importance of the Topic

Trace levels of pesticides and pharmaceuticals in water pose a significant risk to ecosystems and human health. Accurate quantification of these organic contaminants is often hindered by coeluting matrix components that lead to ion suppression or enhancement in electrospray mass spectrometry. Effective removal of matrix interference is therefore essential for reliable monitoring of water quality.

Objectives and Study Overview

This study evaluates an online solid-phase extraction (SPE) approach using the Agilent 1200 Infinity Series coupled to triple quadrupole LC/MS to reduce matrix effects in tap, groundwater, river, and ultrapure water spiked with various pesticides. The performance of online SPE was compared against direct injection in terms of sensitivity, precision, linearity, and matrix interference. A 75 ng/L spike in river water was further assessed using both external calibration and standard addition to determine whether external calibration remains accurate after matrix cleanup.

Methodology and Instrumentation

Samples (ultrapure, tap, groundwater, river water) were centrifuged and maintained at 5 °C prior to injection. A five-level calibration (10 to 200 ng/L) was prepared in each matrix. Online SPE utilized the Agilent 1290 Infinity Flexible Cube with alternating PLRP‐S cartridges for rapid sample loading (up to three solvents) and matrix flushing to waste. Chromatographic separation employed an Agilent ZORBAX SB-AQ column (2.1 × 150 mm, 3.5 µm) at 40 °C with a water/acetonitrile gradient (both containing 0.1% formic acid) and 200 µL injections at 0.5 mL/min.

• Agilent 1290 Infinity Flexible Cube with Online SPE Starter Kit
• Agilent 1260 Infinity Binary Pump and Standard Autosampler
• Agilent 1260 Infinity Thermostatted Column Compartment
• Agilent 6490 Triple Quadrupole LC/MS with Jet Stream technology
• Agilent MassHunter software suite (acquisition, optimization, qualitative, quantitative)

Key Results and Discussion

Online SPE achieved excellent linearity (R2 > 0.991), recoveries between 75–120% and retention time RSDs of 0.1–0.2%. Area precision in river water was typically <10% RSD (n=8). Matrix effects for direct injection showed up to 27% ion suppression for aminocarb in river water and 22% in groundwater. Online SPE reduced suppression to 16% and even slight enhancement (7%) in groundwater. No carryover was observed after cartridge cleaning. When quantifying a 75 ng/L spike in river water, results from external calibration agreed within ±20% of those from standard addition, demonstrating that external calibration remains sufficient after online SPE cleanup.

Benefits and Practical Applications

Online SPE reduces sample handling, solvent usage, and hazardous waste compared with offline SPE. It streamlines workflows by eliminating time-consuming standard addition for most environmental water analyses. The approach enhances throughput, reproducibility, and reliability of trace organic contaminant quantification in routine monitoring and QA/QC laboratories.

Future Trends and Potential Applications

Optimization of loading solvents, flow rates, and cartridge chemistries may further improve matrix removal and sensitivity. The method can be extended to a wider range of polar and nonpolar contaminants, including emerging pollutants. Integration with high-resolution MS and automated data processing will support real-time water quality surveillance and advanced environmental studies.

Conclusion

The Agilent 1200 Infinity Series online SPE solution effectively mitigates matrix effects in environmental water analysis. It delivers robust linearity, precise recoveries, and eliminates the need for complex calibration strategies. External calibration after online SPE cleanup provides accurate quantification of low-level organic contaminants, facilitating efficient and reliable water monitoring.

References

1. Naegele, E. Detection of Basic and Acidic Pesticides and Herbicides at Trace Levels by Online SPE LC/MS in Drinking Water. Agilent Technologies Application Note 5991-4177EN, 2014.
2. Trenholm, R.A.; et al. Online solid phase extraction LC-MS/MS analysis of pharmaceutical indicators in water: A green alternative to conventional methods. Talanta 2009, 79, 1425–1432.
3. Cuadros-Rodriguez, L.; et al. Principles of analytical calibration/quantification for the separation sciences. J. Chromatogr. A 2007, 1158, 33–46.
4. Anumol, T.; Snyder, S.A. Rapid analysis of trace organic compounds in water by automated online solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry. Talanta 2015, 132, 77–86.
5. Thompson, M. Standard additions: myth and reality. Analytical Methods Committee AMCTB No. 37, March 2009.