Determination of Azide in Aqueous Samples by Ion Chromatography with Suppressed Conductivity Detection

Significance of the Topic

Sodium azide is a widely used toxic compound in automotive airbags, laboratory preservatives, agriculture, pharmaceuticals, and forensic investigations. Accurate monitoring of azide in water, food, biological fluids, and buffers is crucial for occupational safety, environmental protection, quality control, and toxicological analysis.

Aims and Study Overview

This work presents a reagent-free ion chromatography (RFIC) method with suppressed conductivity detection for routine determination of azide anion in diverse aqueous samples. The objective is to achieve direct injection without derivatization, high sensitivity (MDL down to 50 µg/L), linear quantification over 0.025–10 mg/L, and minimal interference from common anions.

Methodology and Instrumentation

An isocratic separation using 42 mM KOH eluent generated on-line at 1.2 mL/min and 30 °C was performed on a 4 mm IonPac AG15 guard and AS15 analytical column set. A 25 µL injection and an ASRS ULTRA II suppressor in recycle mode provided suppressed conductivity detection. Samples were simply diluted and filtered to remove particulates before analysis.

Used Instrumentation

• Dionex ICS-3000 RFIC system with Dual Pump, Conductivity Detector, Eluent Generator, Autosampler, and Chromeleon software
• IonPac AG15 guard (4 × 50 mm) and AS15 analytical (4 × 250 mm) columns
• EluGen II KOH cartridge and ASRS ULTRA II suppressor
• 0.2 µm syringe filters

Main Results and Discussion

Calibration curves in reagent water and all tested matrices (tea, orange juice, PBS, urine, plasma) were linear (R² > 0.99) over 0.025–10 mg/L. MDLs ranged from 50 µg/L (water) to 155 µg/L (orange juice). Spike recoveries were 87–117% with precision below 8% RSD. No significant interference was observed from fluoride, chloride, nitrite, sulfate, oxalate, fumarate, nitrate, phosphate, or bromide. Analysis time was 35 min per injection with well-resolved azide peaks.

Benefits and Practical Applications

• Direct sample injection without derivatization
• High sensitivity, precision, and reproducibility
• Reagent-free eluent generation for stable baselines and minimal contamination
• Applicability to environmental, food, clinical, and forensic samples
• Reduced sample preparation and enhanced laboratory throughput

Future Trends and Potential Applications

Future developments may include coupling RFIC with mass spectrometry for improved selectivity, portable and miniaturized IC systems for field use, automated online sampling for real-time monitoring, and multiplexed analysis of azide alongside other analytes in complex matrices.

Conclusion

The RFIC method with suppressed conductivity detection offers a robust, efficient, and sensitive approach for routine azide analysis in diverse aqueous samples, meeting the needs of QA/QC, environmental surveillance, forensic toxicology, and clinical laboratories.

References

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