On-line SPE Enrichment of Trace Organic Contaminants in Water and Juices

Significance of the Topic

This study addresses the critical need for sensitive and high-throughput analysis of trace organic contaminants, including pharmaceuticals and pesticides, in environmental water and juice samples. By automating solid-phase extraction (SPE) directly in line with liquid chromatography–tandem mass spectrometry (LC-MS/MS), the approach improves analyte recovery, reduces operator exposure to hazardous matrices and solvents, and enables overnight and high-frequency sampling without manual intervention.

Objectives and Study Overview

The main goal was to develop and validate an on-line SPE enrichment method using a dual-cartridge Flex Cube configuration coupled to an Agilent 6460 Triple Quadrupole MS for quantifying trace levels (ng/L) of various organic contaminants in surface water and fruit juices. Key performance indicators included linearity, limits of detection (LODs), recovery, and total cycle time.

Methodology

900 µL aliquots of filtered environmental water or juice, spiked with a deuterated internal standard, were loaded onto PLRP-S polymeric cartridges. While one cartridge was in the loading phase, the second underwent elution directly into the LC column using the same mobile-phase solvents. A gradient of water (0.1% acetic acid) and acetonitrile facilitated chromatographic separation on a C8 column at 25 °C and 0.6 mL/min. Mass spectrometric detection employed dynamic MRM in both positive and negative ESI modes, monitoring two transitions per analyte for confirmation.

Used Instrumentation

• Agilent 1290 Infinity Binary Pump with internal degasser
• Agilent 1260 Infinity Autosampler with 900 µL loop and thermostat
• Agilent 1290 Infinity Flexible Cube with two-position/10-port valve
• Agilent 1290 Infinity Thermostatted Column Compartment
• Agilent 6460 Triple Quadrupole LC/MS with Jet Stream technology

Results and Discussion

Recoveries for most analytes ranged from 79% to 115%, with gemfibrozil (35%) and sucralose (41%) as notable exceptions due to sorbent retention and breakthrough issues. LODs spanned 1–500 ng/L, with many compounds detectable below 10 ng/L. Automated cycling reduced per-sample analysis time to under 12 minutes. Application to wastewater-impacted surface water demonstrated simultaneous detection of a dozen target compounds at trace levels, and a preliminary test of lemon juice revealed detectable pesticide residues (e.g., carbendazim, imazalil) with minimal sample handling.

Benefits and Practical Applications

• Enhanced sensitivity through large-volume on-line preconcentration
• Reduced sample handling and operator exposure to hazardous matrices
• Higher throughput and continuous operation, including unattended overnight runs
• Improved reproducibility by eliminating multi-step manual SPE losses

Future Trends and Potential Applications

Future developments may include alternative sorbent chemistries (C18, ion-exchange) to address extreme polarity ranges, automated cleanup steps for complex food matrices like fruit juices, integration with high-resolution mass spectrometry for non-target screening, and system miniaturization for portable environmental monitoring. Adopting greener solvent strategies and advanced valve designs can further enhance sustainability and throughput.

Conclusions

The on-line SPE LC-MS/MS method using the Agilent Flex Cube and Triple Quadrupole platform offers a robust, sensitive, and high-throughput solution for trace organic contaminant analysis in water and small-volume juice samples. Automation streamlines workflow, maximizes analyte recovery, and supports both routine monitoring and research applications.