Sequential injection methodology for carbon speciation in bathing waters.

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Water Quality Monitoring

Background:

• Accurate carbon speciation is crucial for understanding aquatic ecosystems.
• Existing methods for carbon analysis can be complex and time-consuming.
• Inland bathing waters require robust monitoring for environmental health.

Purpose of the Study:

• To develop a novel sequential injection method (SIA) for comprehensive carbon speciation in inland bathing waters.
• To determine dissolved inorganic carbon (DIC), free dissolved carbon dioxide (CO2), total carbon (TC), dissolved organic carbon (DOC), and alkalinity within a single analytical system.
• To validate the SIA method's performance and applicability to real-world water samples.

Main Methods:

• Sequential Injection Analysis (SIA) manifold integrating multiple analytical steps.
• Colorimetric detection using bromothymol blue for DIC, CO2, and TC determination via gas diffusion.
• In-line acidification for DIC and UV photo-oxidation for TC conversion to CO2.
• Spectrophotometric determination of alkalinity using bromocresol green.

Main Results:

• The SIA method successfully determined DIC, CO2, TC, and alkalinity across specified concentration ranges.
• Achieved low limits of detection for DIC (9.5 μg C L⁻¹), CO2 (20 μg C L⁻¹), TC (0.21 mg C L⁻¹), and alkalinity (0.32 mg C L⁻¹).
• Demonstrated good agreement between SIA results and established reference methods when applied to inland bathing waters.

Conclusions:

• The developed SIA method provides an efficient and accurate tool for multi-parameter carbon speciation in inland bathing waters.
• This method simplifies the analytical workflow by integrating multiple determinations into a single manifold.
• The SIA system is a viable alternative to traditional methods for routine water quality monitoring.