Carbon Analysis of Blue-Green Algae Suspensions

Importance of the Topic

Eutrophication from urban and agricultural runoff often triggers cyanobacterial (blue-green algae) blooms in lakes and ponds. These blooms pose health risks due to potential toxins, degrade water quality, and disrupt aquatic ecosystems. Monitoring organic carbon in algal suspensions offers a quantitative indicator of bloom intensity and guides mitigation strategies.

Study Objectives and Overview

This application note demonstrates the measurement of total organic carbon (TOC) in blue-green algae suspensions using Shimadzu’s TOC-L analyzer and the SSM-5000A solid sample combustion unit. Objectives include:

• Quantify carbon concentration in diluted and undiluted algae samples.
• Validate two measurement approaches: liquid TOC analysis and solid sample combustion.
• Assess method suitability for high-turbidity algal suspensions.

Methodology and Instrumentation

Samples were collected from lake water containing cyanobacterial blooms and prepared as follows:

• Diluted Sample: Stock suspension was diluted 1:100 and homogenized ultrasonically for two minutes to break aggregates.
• Stock Sample: Undiluted suspension was placed directly on a ceramic fiber in the solid sample combustion unit.

Instrumentation

• Shimadzu TOC-LCPH Total Organic Carbon Analyzer with catalytic oxidation (900 °C furnace, TC standard catalyst).
• SSM-5000A Solid Sample Combustion Unit for direct analysis of undiluted samples.
• Calibration: Single-point using 100 mgC/L potassium hydrogen phthalate solution for liquid samples and 1% glucose solution for solid samples.

Results and Discussion

• Diluted sample measured by TOC-L yielded 109.7 mgC/L, corresponding to a calculated stock solution concentration of 1.097% C.
• Direct solid sample analysis produced a carbon concentration of 1.075% C in the stock suspension.
• Close agreement between the two methods confirms the reliability of the dilution-homogenization approach and the solid combustion measurement.

Benefits and Practical Applications

• Faster and more accurate than traditional dry weight gravimetric methods for turbid samples.
• Minimal sample preparation: dilution and ultrasonic homogenization suffice.
• Suitable for routine water quality monitoring to track bloom development and inform management decisions.

Future Trends and Potential Uses

• Integration of online TOC monitoring for real-time algae bloom detection.
• Coupling TOC data with remote sensing and machine learning models for predictive water quality management.
• Expansion to other environmental matrices such as sediments or biofilms.

Conclusion

The combined use of Shimadzu’s TOC-L analyzer and SSM-5000A enables reliable determination of organic carbon in blue-green algae suspensions. Both diluted and direct solid sample methods deliver consistent results, offering robust tools for environmental monitoring of eutrophication and cyanobacterial blooms.