Continuous on-line feedback based flow titrations. Complexometric titrations of calcium and magnesium

Area of Science:

• Analytical Chemistry
• Chemical Engineering
• Instrumental Analysis

Background:

• Traditional titration methods can be time-consuming and prone to manual errors.
• Automated titration systems aim to improve accuracy, reproducibility, and throughput.
• Continuous flow analysis offers advantages in sample handling and reaction control.

Purpose of the Study:

• To develop and validate a continuous feedback-based flow titration method for determining calcium and magnesium ions.
• To apply the principle of compensating errors in a flow system for enhanced analytical accuracy.
• To achieve high-throughput and reproducible results in ion determination using EDTA titrant.

Main Methods:

• Utilized continuous feedback-based flow titrations with a constant total flow rate (F(T)).
• Employed a metal ion indicator and optical detector to monitor the equivalence point in the mixed stream.
• Implemented a controller that adjusted titrant (EDTA) flow based on optical feedback, generating a triangular waveform.

Main Results:

• Achieved good reproducibility with relative standard deviations (R.S.D.) ranging from 0.2% to 0.7%.
• Demonstrated high throughput, with each titration taking only 33-42 seconds.
• Successfully determined calcium and magnesium ions using the developed flow titration system.

Conclusions:

• The continuous feedback-based flow titration methodology is effective for accurate and rapid ion determination.
• The error compensation principle and sensor-governed control enhance the reliability of the titration process.
• This approach offers a significant improvement in analytical efficiency for complex sample matrices.