Novel approaches to analysis by flow injection gradient titration.

Area of Science:

• Analytical Chemistry
• Spectrophotometry
• Titration Techniques

Background:

• Traditional titration methods can be time-consuming and require multiple standard solutions.
• Developing efficient and accurate analytical procedures is crucial for chemical analysis.
• Flow injection analysis offers potential for automated and rapid chemical measurements.

Purpose of the Study:

• To introduce two novel flow injection gradient titration procedures: multi-point single-line (MP-SL) and single-point multi-line (SP-ML).
• To demonstrate the utility of these methods using a single stock standard solution for constructing calibration graphs.
• To evaluate the precision and accuracy of the proposed methods for acid-base titrations.

Main Methods:

• MP-SL method: Calibration graph constructed from standard solutions generated in a reservoir and injected into the titrant.
• SP-ML method: Standard solution and sample injected into the titrant stream from multiple loops of different capacities.
• Spectrophotometric acid-base titration of hydrochloric and acetic acids using bromothymol blue and phenolphthalein indicators with sodium hydroxide titrant.

Main Results:

• MP-SL procedure achieved precision <1.8% RSD and accuracy <3.0% RE for hydrochloric acid (0.0031-0.0631 mol L⁻¹).
• SP-ML procedure achieved precision <2.5% RSD and accuracy <5.4% RE for acetic acid (0.1680-1.7600 mol L⁻¹).
• Both methods demonstrated feasibility in determining total acidity in vinegar samples with high precision (<0.5% RSD for MP-SL, <2.9% RSD for SP-ML).

Conclusions:

• The proposed MP-SL and SP-ML methods are effective for flow injection gradient titration using a single standard solution.
• These novel procedures offer reliable and accurate results for acid-base titrations across various concentration ranges.
• The methods are practical for real-world applications, such as analyzing acidity in food products like vinegar.