Analysis of Semivolatile Compounds in Water

Significance of the Topic

The presence of semivolatile organic compounds (sVOCs) in water sources poses significant risks to human health and aquatic ecosystems. Regulatory frameworks in the European Union set stringent limits for these pollutants in drinking and surface waters. Achieving reliable detection at sub-nanogram-per-liter levels is essential for compliance, risk assessment, and environmental monitoring.

Objectives and Study Overview

This study presents a fast, cost-effective low-density liquid-liquid microextraction (LDME) procedure combined with Agilent 7010 triple quadrupole GC/MS for multiresidue analysis of sVOCs. Method performance was validated according to ISO/IEC 17025 guidelines, including assessments of linearity, sensitivity, precision, recovery, and carryover. Interlaboratory proficiency tests compared LDME results with those from Stir Bar Sorptive Extraction (SBSE) and Solid Phase Extraction (SPE) in both drinking and high-organic-load surface water samples.

Methodology and Instrumentation

The LDME protocol uses 15 mL water spiked with isotopically labeled standards, followed by addition of 150 µL toluene. Sample agitation in a vortex mixer creates microdroplets that rapidly extract sVOCs. For low-organic matrices, a brief centrifugation separates phases; for turbid samples, the aqueous layer is frozen at –30 °C and the upper organic phase is decanted into a GC vial. A 4 µL injection of toluene extract is analyzed by GC/TQ in dynamic multiple reaction monitoring mode. Calibration spans seven levels tailored to meet EU parametric values for pesticides and polycyclic aromatic hydrocarbons.

Used Instrumentation

• Agilent 8890 Gas Chromatograph
• Agilent 7010 Triple Quadrupole GC/MS with High-Efficiency Ion Source
• Agilent 7693 Automatic Liquid Sampler
• Standard laboratory vortex mixer, centrifuge, and cryothermostat

Main Results and Discussion

Linearity across all 145 target sVOCs was excellent (R² > 0.99) with residuals within ±20%. Limits of detection and quantitation were routinely below 1 ng/L. Repeatability (n = 10) and reproducibility (n = 150) studies showed recoveries between 90 % and 120 % and precision below 20 % RSD. Instrumental carryover was negligible (< 0.14 %). Proficiency tests yielded z-scores under 1 for over 85 % of analytes when compared to SBSE and SPE, confirming quantitative agreement even in high-organic matrices without centrifugation.

Benefits and Practical Applications

The LDME GC/TQ workflow reduces solvent and sample volumes, uses disposable consumables to minimize cross-contamination, and avoids chlorinated solvents. It lowers per-sample cost, simplifies sample handling, and accelerates throughput. The approach fulfills EU regulatory requirements for drinking and surface water analysis and is ideal for routine QA/QC in environmental laboratories.

Future Trends and Potential Applications

Further automation and miniaturization of LDME could enhance throughput and reproducibility. Integrating online extraction and direct coupling with high-resolution MS or alternative detectors may broaden applicability to emerging contaminants. On-site portable GC/TQ systems using LDME cartridges could enable real-time water quality monitoring. Expansion to other complex matrices, such as wastewater or food, will extend the method's utility.

Conclusion

The LDME combined with Agilent 7010 triple quadrupole GC/MS provides a robust, sensitive, and economical solution for multiresidue analysis of semivolatile compounds in water. Validated per ISO/IEC 17025 and demonstrated through interlaboratory comparisons, the method ensures compliant, reliable measurements at sub-ng/L levels, with minimal carryover and matrix interference.

Reference

1. European Parliament and Council. Directive (EU) 2020/2184 on the quality of water intended for human consumption. Official Journal of the European Union, L 435.
2. European Parliament and Council. Directive 2000/60/EC establishing a framework for Community action in the field of water policy. Official Journal of the European Communities, L 327.
3. European Parliament and Council. Directive 2008/105/EC on environmental quality standards in the field of water policy. Official Journal of the European Union, L 348.
4. European Parliament and Council. Directive 2013/39/EU amending Directives 2000/60/EC and 2008/105/EC as regards priority substances. Official Journal of the European Union, L 226.
5. Council of the European Union. Council Directive 98/83/EC on the quality of water intended for human consumption. Official Journal of the European Union, L 330.
6. International Organization for Standardization. ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories.