Determination of Perchlorate in Vegetation Samples Using Accelerated Solvent Extraction and Ion Chromatography

Importance of the Topic

Perchlorate contamination of soil and vegetation poses a significant health risk by disrupting thyroid function through iodide uptake inhibition. Its high solubility and persistence lead to widespread environmental distribution, especially near military and industrial sites. Sensitive and efficient methods for measuring trace perchlorate in plant matrices are essential for monitoring and remediation efforts.

Objectives and Study Overview

This study aimed to develop a rapid, automated method for extracting and quantifying perchlorate in vegetation and soil using accelerated solvent extraction (ASE) coupled with ion chromatography (IC). Key goals included assessing extraction efficiency, method precision, detection limits, and applicability across diverse matrices such as soil, alfalfa, corn, melon, spinach, and milk.

Methodology and Instrumentation

The extraction protocol employed water as the sole solvent in a Thermo Scientific Dionex ASE 200/300 system. Sample cells were packed with precleaned matrix, basic alumina, and various Dionex OnGuard ion-exchange resins for in-cell cleanup. ASE parameters included 80 °C, 1 500 psi, three static cycles of 5 min each, followed by solvent flush and nitrogen purge. Extracts were filtered (0.2 µm) and analyzed by ion chromatography on a Thermo Scientific Dionex ICS-2500 system. Key chromatographic conditions:

• Columns: IonPac AS16 analytical, AG16 guard, Cryptand C1 concentrator
• Eluent: Gradient NaOH (0.5, 65, 100 mM)
• Flow rate: 0.25 mL/min, temperature: 35 °C
• Detection: Suppressed conductivity with ASRS ULTRA II (100 mA)

Main Results and Discussion

Recoveries for soil, alfalfa, corn, milk, melon, and spinach ranged from 88 to 119 % with RSDs below 9 %. Lower-level spikes (10, 50, 200 ppb) in corn, melon, and spinach yielded recoveries of 96–110 % (RSD 2.5–8.9 %). Method detection limits (MDL) were 0.7–2.0 µg/kg, and reliable quantitation limits (RQL) were 2.9–8.0 µg/kg. Chromatograms showed no significant matrix interferences, demonstrating the effectiveness of in-cell cleanup and preconcentration.

Benefits and Practical Applications

ASE with water simplifies sample preparation, reducing solvent use, extraction time (<15 min/sample), and manual labor compared to blending or sonication. In-cell ion-exchange cleanup eliminates extensive post-extraction steps. The method supports high throughput (up to 24 samples per run) and delivers ppb-level detection for vegetation monitoring, regulatory compliance, and environmental research.

Future Trends and Applications

Advances may include coupling ASE with mass spectrometric detection for enhanced specificity and lower detection limits. Miniaturized and field-deployable ASE systems could enable on-site analysis. Integration with automated data processing and online QC will accelerate large-scale environmental surveys and remediation monitoring.

Conclusion

The ASE–IC method provides a robust, rapid, and reproducible approach for perchlorate determination in complex matrices. Its high recoveries, low detection limits, and reduced labor make it well suited for environmental monitoring and regulatory applications.

References

1. Q. Cheng et al., Talanta, 2005.
2. W. A. Jackson et al., J. Agric. Food Chem. 2005, 53, 369.
3. U.S. EPA Method 314.1, 2005.