Determination of benzoate in soy sauce using a compact IC system

Significance of the Topic

The preservation of acidic foods such as soy sauce relies on benzoate additives to inhibit microbial growth. Regulatory authorities set strict maximum limits to ensure consumer safety: the FDA permits up to 0.1% sodium benzoate, while the EU allows up to 1,000 mg/kg total benzoic acid and salts in sauces. Reliable analytical methods are essential to verify compliance and maintain product quality.

Study Objectives and Overview

This application proof note demonstrates a compact ion chromatography (IC) system for the quantification of benzoate in soy sauce. The study adapts a Dionex Inuvion IC configuration with updated eluent generation and suppressor technology to deliver accurate, precise, and high-throughput analysis.

Methodology

A soy sauce sample was diluted 20-fold and analyzed alongside standards of 1–20 mg/L benzoate. The method employed a gradient of KOH eluent (35–50 mM) over a 20-minute run. Calibration was established by triplicate injections at each standard level, yielding linear response (r2 = 0.99985). Key operating parameters included a 25 µL injection, 1.0 mL/min flow rate, and 30 °C column temperature.

Instrumentation

• Dionex Inuvion IC system with pump degas module and eluent generation
• Dionex IonPac AS18 anion-exchange column (4 × 250 mm)
• Dionex AS-DV autosampler with 5 mL vials and filter caps
• EGC 500 KOH eluent cartridge and CR-ATC 600 anion trap column
• RFIC eluent degasser and ADRS 600 suppressor operating at 124 mA in recycle mode
• Chromeleon CDS software version 7.3.2

Main Results and Discussion

The 20-fold diluted soy sauce contained 6.89 mg/L benzoate, corresponding to 0.0138% (134 mg/kg) expressed as benzoic acid—well below both FDA and EU limits. Chromatograms showed clear separation of chloride, phosphate, benzoate, and citrate peaks. Additional food matrices (diet cola, lemon juice, browning sauce) were analyzed at dilution factors up to 500-fold, confirming method robustness across diverse samples.

Benefits and Practical Applications

• High sensitivity and selectivity for benzoate in complex matrices
• No external reagents required for eluent preparation
• Minimal sample preparation and fast turnaround (20 min per run)
• Compliance with regulatory requirements for food safety testing
• Scalable for routine QA/QC in industrial and research laboratories

Future Trends and Opportunities

Emerging developments may include integration with mass spectrometry for enhanced specificity, further miniaturization of IC systems for field testing, and automated sample handling to boost throughput. Advanced data analytics could enable predictive quality control and real-time monitoring of food safety parameters.

Conclusion

The compact IC system with reagent-free eluent generation and modern suppression technology delivers a reliable, efficient, and compliant method for benzoate determination in soy sauce and related food products. This workflow supports stringent regulatory verification and routine quality assurance.

References

1. U.S. FDA. Food Additive Status List. Accessed May 2023.
2. EU Commission Regulation (EU) No 1129/2011. Annex II. Accessed May 2023.
3. Thermo Scientific Application Note 165: Determination of benzoate in liquid food products by Reagent-Free™ ion chromatography. 2016. Accessed May 2023.