Analysis of phthalate esters in environmental water samples by online-SPE-LC coupled with high-speed triple quadruple mass spectrometer

Importance of the Topic

Phthalate esters are widely used plasticizers and recognized as environmental contaminants with endocrine disrupting potential. They may transform into monoesters and migrate from wastewater into surface and ground water, posing potential health and ecological hazards. Sensitive, rapid and reliable analysis of both diesters and monoesters at trace levels supports risk assessment, regulatory compliance and water quality monitoring.

Objectives and Overview of the Study

This study aimed to develop a fast online solid-phase extraction (SPE) coupled liquid chromatography (LC) method combined with a high-speed triple quadrupole mass spectrometer for simultaneous quantification of phthalate diesters and monoesters in environmental water samples. The goal was to minimize background contamination and achieve a high-throughput 15-minute cycle.

Methodology

• Online-SPE Setup: A preparative SPE column captured analytes from 1 mL water samples automatically injected and directed through a scrubber column to remove interferences.
• Chromatographic Separation: Analytical separation on a Shim-pack XR-ODSII column (2 × 75 mm, 2.2 μm) using a gradient of 0.1% formic acid in water and acetonitrile at 0.25 mL/min and 40 °C.
• Mass Spectrometry: ESI polarity switching (10 ms) for positive-mode detection of diesters and negative-mode detection of monoesters. MRM transitions were optimized for each compound.
• System Cleaning: Simultaneous SPE column washing and flow-line purging limited carryover and reduced background peaks from valves and the autosampler.

Used Instrumentation

• LCMS-8030 triple quadrupole mass spectrometer
• Shimadzu SIL-10AP autosampler with 5 mL syringe
• Shim-pack XR-ODSII scrubber and analytical columns
• ENV-MASK preparative SPE column

Main Results and Discussion

The method achieved a 15-minute total runtime, including online-SPE and LC separation. High-speed polarity switching enabled simultaneous analysis of 13 target phthalate compounds. Use of a scrubber column significantly reduced background contamination, although autosampler and valve components remained minor sources. Recoveries at 500 ng/L spiked in river water ranged from 53% to 134% with relative standard deviations below 20%. Calibration curves were linear across 2–10 000 ng/L with R² values above 0.997.

Benefits and Practical Applications of the Method

• High-throughput analysis with minimal manual handling supports routine monitoring of phthalates in water treatment and environmental surveys.
• Simultaneous quantification of diesters and monoesters reduces analysis time and resource consumption.
• Enhanced sensitivity and reduced background interference improve trace-level detection for regulatory compliance.

Future Trends and Opportunities

Ongoing work will assess long-term SPE column stability and lifetime for extended monitoring campaigns. Integration with automated data processing and expansion to additional polar metabolites can further improve water quality assessments. Adapting similar online-SPE-LC-MS/MS workflows to emerging contaminants will enhance broad-spectrum environmental screening.

Conclusion

A novel online-SPE-LC-MS/MS approach was established for efficient, sensitive and rapid analysis of phthalate di- and monoesters in environmental waters. The method delivers reliable quantitation with minimized background interference and a 15-minute cycle time, offering a robust tool for environmental monitoring and quality control.