Highly Sensitive Determination of Contaminants in Surface Water in the Context of the EU Water Framework Directive using Stir Bar Sorptive Extraction (SBSE) and GC-MS/MS

Importance of the Topic

The European Union Water Framework Directive (2000/60/EC and its amendments) requires sensitive, reliable monitoring of priority pollutants in surface and coastal waters to protect aquatic ecosystems and human health. Meeting stringent environmental quality standards (EQS) at sub-ng/L to pg/L levels poses analytical challenges, especially for trace persistent organic pollutants (POPs), pesticides and particle-adsorbed compounds. A robust method combining stir bar sorptive extraction (SBSE) with GC-MS/MS addresses these needs while minimizing sample volume and handling.

Objectives and Study Overview

This work aimed to develop and validate a single-run analytical procedure for around 100 EU-listed contaminants in 100 mL surface water samples. Key goals were:

• Achieve limits of quantification (LOQs) at or below 30 % of the relevant EQS for inland surface waters
• Include polar, nonpolar, volatile, nonvolatile and particle-bound analytes
• Ensure method simplicity, repeatability (RSD < 15 %) and trueness within 90–110 %
• Demonstrate applicability to real environmental and treated effluent samples

Applied Methodology

A sequential SBSE approach was used with GERSTEL Twister® PDMS stir bars:

• Step 1: 100 mL sample + 30 µL internal standards, stirred at 1 000 rpm for 5 h
• Step 2: Addition of 15 mL organic modifier, second Twister extraction at 1 000 rpm and elevated temperature for 17 h
• Twisters rinsed, dried under nitrogen, then combined in a thermal desorption tube

Automated thermal desorption in a GERSTEL TDU/CIS transferred analytes to an Agilent 7890 GC with HP-5ms column and Agilent 7010 triple quadrupole in MRM mode. Quadratic and linear calibrations spanned 50–200× LOQ with matrix-matched standards.

Used Instrumentation

• GERSTEL MultiPurpose Sampler (MPS) with TDU 2 and CIS 4
• GERSTEL Twister® PDMS stir bars (1 cm × 1 mm)
• Agilent 7890B GC coupled to 7010 triple quadrupole MS
• HP-5ms Ultra Inert column (30 m × 0.25 mm × 0.25 µm)
• Helium carrier gas, N₂ collision gas, He quench gas

Main Results and Discussion

Validation against EU-WFD inland surface water criteria showed:

• LOQs from ~0.01 to 10 ng/L for most analytes; only cypermethrin, heptachlor and its epoxides missed the target
• RSD 1–15 % (avg. 6.9 %) and trueness 90–110 %
• Expanded uncertainty < 50 % at EQS levels
• Accurate quantification of particle-bound PAHs and organochlorine pesticides using certified sediment reference material
• Successful application to river, ground, tap, mineral water and sewage effluents, detecting multiple pesticides, PAHs, PCBs and PBDEs

Benefits and Practical Applications

This method offers:

• Low sample volume (100 mL) with high sensitivity for routine monitoring
• Broad analyte scope including particle-adsorbed compounds
• Minimal manual steps and full automation for high throughput
• Compliance with EU-WFD LOQ and performance requirements

Future Trends and Applications

Further enhancements may include negative chemical ionization for ultra-low LOQs, expanded analyte lists, green solvent modifiers, in-field SBSE sampling, integration with data analytics and machine learning for pattern recognition, and miniaturized automated platforms for decentralized water monitoring.

Conclusion

A sequential SBSE GC-MS/MS method using GERSTEL Twister and Agilent 7010 QQQ provides a reliable, sensitive and automated solution for compliance-driven trace analysis of surface waters. It fulfills EU-WFD requirements for nearly all priority pollutants and supports routine environmental and industrial water quality control.

References

• Directive 2000/60/EC establishing a framework for water policy
• Directive 2008/105/EC on environmental quality standards
• Directive 2013/39/EU amending priority substances
• Commission Directive 2009/90/EC on chemical analysis specifications
• Commission Implementing Decision (EU) 2015/495 watch list
• OGewV (July 2011) German surface water ordinance
• N. Ochiai et al., Sequential SBSE for uniform enrichment, GERSTEL AppNote 12/2008
• DIN 32645:2008-11 on detection and quantification limits
• Uncertainty calculation freeware, Univ. Stuttgart