Determination of selected herbicides and their degradation products in water

Importance of the Topic

Pesticide residues and their degradation products in drinking and ground water must be monitored at submicrogram per liter levels to meet stringent EU regulations. Precise, accurate and sensitive analytical methods are essential for ensuring water safety and compliance with legal limits.

Objectives and Study Overview

This study aimed to develop and validate a solid phase extraction gas chromatography mass spectrometry method with deuterated internal standards for the determination of selected herbicides and their transformation products in water samples. It targeted compounds such as atrazine, terbutylazine, simazine, metolachlor and hexachlorobenzene among others.

Methodology

Samples of spring water and groundwater were processed by SPE using 200 mg cartridges. Each 1.15 L sample was spiked with deuterated standards at a target level of 100 ng/L. Cartridges were dried, eluted with dichloromethane, dried over sodium sulphate and concentrated under nitrogen. Analytes were redissolved in acetone or acetone DCM and injected splitless.

Calibration involved two ranges to cover low and high concentration levels with area ratio versus mass ratio regression. Quality control included daily control runs and system stability checks.

Instrumentation Used

Shimadzu GC 17A with QP 5050A mass spectrometer and AOC 20i autosampler was employed. A DB 5MS capillary column (30 m x 0.25 mm) and silanized injection liners ensured system stability. High purity helium and nitrogen were used as carrier and collision gases.

Results and Discussion

The method achieved limits of detection down to 1 ng/L for many analytes and a working range up to 600 ng/L. Expanded uncertainty was approx 10 percent at 100 ng/L. Statistical analysis confirmed linearity, precision and accuracy according to ISO EN 17025, EU guidelines and EPA methods. Interlaboratory comparisons yielded results within acceptable ranges.

Benefits and Practical Applications

This SPE GCMS approach is highly suitable for regulatory monitoring of semi volatile organic compounds in water at stringent levels. It enables trend analysis and groundwater transport studies using herbicides as natural tracers. The use of deuterated standards compensates for matrix and instrument variability.

Future Trends and Potential Applications

Future developments may include the use of additional deuterated standards, automation of SPE processes, miniaturized extraction formats and coupling with high resolution mass spectrometry. Expanding the analyte list and integrating non target screening can further enhance environmental monitoring capabilities.

Conclusion

The validated SPE GCMS method with internal deuterated standards provides a robust, accurate and precise tool for the determination of herbicide residues and degradation products in water. It complies with regulatory requirements and offers reliable data for water quality assessment.

References

1. EURAU position paper EU1 01 A56 Keeping Raw Drinking Water Resources Safe from Pesticides 2001
2. Quality control procedures for pesticide residues analysis Guidelines for Residues Monitoring in the European Union 2003
3. Organic Compounds by Liquid Solid Extraction and Capillary Column GC MS EPA Method 525 2 Rev 2 0
4. Determination of Selected Semi volatile Organic Compounds in Drinking Water by SPE and GC MS EPA Method 526 1 Rev 1 0
5. Shimadzu application note SCA 280 004
6. Macherey Nagel application note No 155
7. R Soniassy P Sandra C Schlett Water Analysis Organic Micropollutants Hewlett Packard 1994
8. Methods of Analysis by the US Geological Survey Organic Geochemistry Research Group Determination of Selected Herbicides Metabolites and Their Degradation Products in Water Using SPE GC MS
9. P Auersperger J Kus B Gorenc Slovenski kemijski dnevi 2000
10. P Auersperger J Kus Slovenski kemijski dnevi 2003
11. ASTM D4128 01
12. Eurachem Citac Guide to Quantifying Uncertainty in Analytical Measurement Second Edition 2000
13. ISO 10843 2 2000
14. EURACHEM CITAC guide Traceability in Chemical Measurement 2003
15. EURACHEM CITAC Guide to achieving comparable results in chemical measurement 2003
16. ISO 17025