Barium analysis by automated photometric titration

Significance of the Topic

Accurate quantification of barium in aqueous samples is critical across environmental monitoring, industrial process control and quality assurance in pharmaceuticals and water treatment. Automated photometric titration with EDTA offers a robust, reproducible approach that minimizes operator error and accelerates throughput.

Objectives and Study Overview

The application note demonstrates an automated method for determining barium concentration in alkaline media using direct titration with EDTA. The use of phthalein purple as an indicator and photometric endpoint detection at 574 nm aims to optimize precision and simplify routine analysis.

Methodology and Instrumentation Used

Sample Preparation and Reagents

• No sample pretreatment required for aqueous barium solutions (0.05 mol/L).
• EDTA titrant: 0.10 mol/L Na₂EDTA solution, preferably commercially prepared.
• Indicator: 50 mg phthalein purple dissolved in 40 mL deionized water with 1 mL of 25 percent ammonia, diluted to 50 mL.

Instrumentation Configuration

• Titrator: Metrohm 907 Titrando with swing head and robotic sample processor (815 XL).
• Dosing: Dosino units of 5, 10 and 50 mL capacity.
• Endpoint detection: Optrode photometric sensor at 574 nm.
• Control parameters: MET U mode, volume increments of 0.05 mL, endpoint criterion 15 mV, greatest slope recognition, stirring rate 8, pause 30 s.

Procedure

1. Pipette 5–15 mL of sample into a 200 mL polypropylene beaker and dilute with 90 mL deionized water.
2. Add 5 mL of 25 percent ammonia and 0.5 mL indicator solution.
3. Perform titration with 0.10 mol/L EDTA until the photometric endpoint is reached.

Main Results and Discussion

Six replicate titrations yielded a mean barium concentration of 6.943 g/L with a relative standard deviation of 0.52 percent. The automated sequence provided consistent endpoint detection and low drift under the optimized settings. The combination of precise dosing increments and photometric sensing resulted in high analytical reliability.

Benefits and Practical Applications

Key advantages of this automated titration method include:

• High precision and reproducibility suitable for regulated QA/QC laboratories.
• Minimal sample handling and simplified reagent preparation.
• Reduced analysis time and operator intervention.
• Adaptability to a variety of aqueous matrices.

Future Trends and Applications

Emerging developments may include integration of advanced chemometric algorithms for real-time endpoint refinement, miniaturized flow-through titration systems for field use, and coupling with complementary detectors such as ion selective electrodes or fluorescence sensors. Connectivity with laboratory information management systems will further streamline data handling and compliance.

Conclusion

The automated photometric titration method using EDTA and phthalein purple indicator provides a fast, precise and reproducible approach for barium determination in alkaline solutions. Its reliable performance and ease of operation make it a valuable tool for diverse analytical laboratories.

References

None specified in the original application note.