Determination of Perchlorate in High Ionic Strength Fertilizer Extracts by Ion Chromatography

Significance of the Topic

The analysis of perchlorate in environmental and industrial matrices is critical due to its persistence, mobility, and interference with thyroid hormone synthesis. Reliable detection at trace levels in high ionic strength samples such as fertilizer extracts supports environmental monitoring, regulatory compliance, and quality control in agriculture.

Objectives and Study Overview

This application note describes a rapid, robust ion chromatography method using a high-capacity anion exchange column and on-line generated hydroxide eluent for the determination of perchlorate in complex fertilizer extracts. The objectives are:

• Develop a 15-minute isocratic separation for perchlorate in high ionic strength samples.
• Achieve detection limits comparable to EPA Method 314.0.
• Demonstrate method performance across diverse fertilizer matrices.

Methodology

Solid and liquid fertilizer samples were extracted with reagent water, shaken, centrifuged, and filtered. High chloride matrices were optionally treated with Ag and H OnGuard cartridges to remove chloride. The analytical system comprised:

• Dionex IonPac AS16 analytical and AG16 guard columns.
• EG40 eluent generator producing 65 mM KOH.
• DX-600 system with suppressed conductivity detection (ASRS ULTRA in gas-assisted external water mode).
• Partial-loop 500 µL injection.

Main Results and Discussion

Calibration was linear from 3 to 200 µg/L perchlorate (R²=0.9996). The method detection limit (MDL) was 0.43 µg/L. Spike recoveries in various matrices ranged from 96 % to 110 % after appropriate dilutions (100- to 10 000-fold). Potential coelution of polyphosphates was examined; at 65 mM KOH, perchlorate was well resolved from pyrophosphate and tripolyphosphate. System performance and column maintenance guidelines were provided to ensure stable retention times and minimize fouling.

Benefits and Practical Applications

This method enables:

• Rapid, high-throughput screening of perchlorate in fertilizers and related materials.
• Accurate quantification in high ionic strength samples without extensive cleanup.
• Reduced reagent consumption via on-line eluent generation and gas-assisted suppressor operation.

Future Trends and Potential Applications

Future improvements may include higher-capacity columns, advanced suppressor technologies to further reduce maintenance, and coupling with mass spectrometry for enhanced selectivity. Expanded monitoring of other polarizable anions in environmental and industrial samples is anticipated.

Conclusion

The presented ion chromatography method offers a reliable, sensitive, and efficient solution for perchlorate analysis in high-ionic strength fertilizer extracts. It meets regulatory requirements and supports comprehensive monitoring of environmental and agricultural materials.

Instrumentation Used

• Thermo Scientific Dionex DX-600 chromatography system (GP50 pump, EG40 eluent generator, ED50 detector, AS50 autosampler).
• Dionex IonPac AG16 guard and AS16 analytical columns.
• Dionex EluGen Hydroxide cartridges (EGC-KOH) and SRS gas-assisted regeneration kit.
• DS3 suppressor cell, orbital shaker, centrifuge, and 0.2 µm IC syringe filters.

References

1. Jackson P.E. et al., Journal of Chromatography A, 888 (2000) 151.
2. U.S. EPA Method 314.0, Determination of Perchlorate in Drinking Water by Ion Chromatography, 1999.
3. Dionex Application Note 134, Determination of Low Concentrations of Perchlorate in Water, 2000.
4. U.S. EPA Survey of Fertilizers for Perchlorate, EPA/600/R-01/049, 2001.
5. ASTM D5679-95A and E300-92, Standard Practice for Sampling Industrial Chemicals.
6. U.S. EPA Method 300.0, Inorganic Anions in Water by Ion Chromatography, 1993.
7. Madden J.E. et al., Journal of Chromatography A, 837 (1999) 65.