Measurement of TOC in High-Salt Sample with High-Salt Sample Combustion Tube Kit

Importance of the Topic

The measurement of total organic carbon (TOC) in high-salt matrices such as seawater plays a critical role in assessing marine organic pollution and monitoring environmental health. Direct analysis without dilution or complex pretreatment streamlines sample processing and enhances result reliability.

Study Objectives and Overview

This study evaluates the performance of a high-salt sample combustion tube kit installed in the Shimadzu TOC-LCSH analyzer for direct TOC measurement in sodium chloride solutions. By spiking 3.5% NaCl solutions with potassium hydrogen phthalate at various concentrations (0.2–2.0 mgC/L), the research aims to verify accuracy, extend maintenance intervals, and reduce operational costs.

Methodology and Instrumentation

The analytical setup included:

• Shimadzu TOC-LCSH Total Organic Carbon Analyzer equipped with a high-salt sample combustion tube kit and B-type halogen scrubber
• High-salt sample catalyst with larger particle size to mitigate salt clogging
• Injection volume set to 150 µL per sample
• Measurement mode: NPOC (acidification and sparging)
• Two-point calibration using potassium hydrogen phthalate standards at 0 and 3 mgC/L with shift-to-origin correction
• Reagents: Sodium chloride for matrix simulation and high-grade potassium hydrogen phthalate as the carbon spike

Main Results and Discussion

Baseline analysis of the 3.5% NaCl solution yielded a TOC background of approximately 0.083 mgC/L due to residual carbon in the matrix. Spiked samples exhibited linear recovery, with measured TOC values closely matching theoretical concentrations plus the baseline shift. For example, a 0.2 mgC/L spike resulted in a measured value of about 0.289 mgC/L, demonstrating accurate quantitation across the tested range.

Benefits and Practical Applications

• Direct TOC analysis in saline matrices without dilution or additional pretreatment
• Extended combustion tube and catalyst lifetime, enabling up to 2500 measurements with minimal maintenance
• Reduced operational costs and downtime for routine seawater monitoring
• High accuracy and reproducibility in quantifying low-level organic carbon

Future Trends and Opportunities

Advancements may include adapting this high-salt approach to other challenging matrices such as brine or industrial effluents, integrating automated sample handling, and coupling TOC analysis with complementary techniques for comprehensive water quality assessment.

Conclusion

The implementation of a high-salt sample combustion tube kit in TOC analysis offers a robust solution for accurate, cost-effective determination of organic carbon in high-saline samples. The method significantly reduces maintenance requirements and supports reliable monitoring of marine environments.

References

No external references were cited in the original application note.