Mass Spectrometry Applications for Environmental Analysis

Significance of the Topic

Emerging organic wastewater contaminants (OWCs) such as pharmaceuticals, personal care products, and pesticides are increasingly detected in surface and drinking waters.
Traditional analyses often require large sample volumes and laborious offline preparation, limiting throughput and reproducibility.
A simplified, high-sensitivity workflow is needed to monitor these trace compounds in water resources.

Goals and Study Overview

Develop a unified method combining online SPE preconcentration, reversed-phase LC, and LC-MS/MS for simultaneous detection of diverse antibiotic, pesticide, and personal care product residues.
Apply positive APCI triple quadrupole MS/MS for simultaneous quantitation and confirmation of 14 antibiotics in drinking water at pg/mL levels.

Methodology and Instrumentation

Sample Preparation:

• Direct SPE of 1 L water through 200 mg C18 cartridge (MTBE/MeOH elution, N₂ evaporation, reconstitution in 200 µL aqueous 0.1% formic acid/MeOH with internal standards).

Chromatography:

• EQuan MAX online SPE–HPLC system; trapping column Hypersil GOLD aQ (20×2.1 mm); analytical Accucore aQ (100×2.1 mm); two-pump gradient; 15 min total run time.

Mass Spectrometry:

• Thermo Scientific TSQ Quantum Access Ultra triple quadrupole; APCI source for broad compound coverage; SRM transitions optimized for 14 antibiotics.

Data Processing:

• TraceFinder for quantitation with 5 ppm mass tolerance, linear/quadratic calibration with 1/X weighting.
• ExactFinder for spectral confirmation of MS² (HCD) against reference libraries.

Main Results and Discussion

Limits of quantitation ranged from 0.2 to 40 pg/mL with %RSD < 15%.
Solid-phase extraction and APCI-MS/MS allowed sub-ppt sensitivity without offline concentration.
Linear calibrations achieved over three orders of magnitude.
Spectral matching of MS² fragments confirmed the identity of low-level analytes.

Benefits and Practical Applications

Single-run, multi-class analysis of antibiotics at pg/mL levels with minimal sample prep.
APS injection volumes reduced from liters to 1 L SPE, improving sample handling.
Enhanced throughput and reproducibility for environmental water monitoring.
Robust APCI ionization reduces matrix suppression for steroid-like and nonpolar analytes.

Future Trends and Possibilities

Extend the workflow to broader classes of OWCs including pesticides and steroids.
Integrate high-resolution MS workflows (e.g., Orbitrap) for non-target screening in the same run.
Automate calibration and data review with advanced software tools.
Explore isotope-labeled internal standards to correct for matrix effects.
Develop real-time monitoring applications with online SPE–MS coupling in the field.

Conclusion

A streamlined APCI-LC-MS/MS method using online SPE enables sensitive, simultaneous quantitation and confirmation of multiple antibiotics in drinking water.
The approach eliminates offline concentration, reduces sample volumes, and achieves pg/mL detection limits with robust reproducibility.

Reference

• No references provided in the original text.