Titration without Mixing or Dilution:  Sequential Injection of Chemical Sensing Membranes.

Area of Science:

• Analytical Chemistry
• Chemical Engineering
• Materials Science

Background:

• Traditional titration methods can involve complex mixing and dilution steps.
• Miniaturization in analytical chemistry offers potential for increased efficiency and reduced sample/reagent consumption.
• Developing novel sensing materials is crucial for advancing analytical techniques.

Purpose of the Study:

• To develop and validate a miniaturized titration system for determining acid concentration.
• To utilize agarose beads as a semisolid aqueous titrant carrier within a nonaqueous sample stream.
• To establish a robust and efficient analytical method for acid quantification.

Main Methods:

• A novel titration system was designed using 35 μm diameter agarose beads containing aqueous sodium hydroxide (NaOH) titrant and a pH indicator.
• The agarose beads were packed into a flow cell and perfused with sulfuric acid (H2SO4) in 1-butanol samples.
• Transmittance measurements were conducted via fiber optics, monitoring the pH indicator's response to the titration reaction.

Main Results:

• The system successfully employed agarose beads as a semisolid titrant, retaining NaOH within a nonaqueous sample stream.
• Automated packing and disposal of bead layers enabled irreversible reactions and efficient analysis.
• A linear relationship (R² = 0.9980) was observed between the endpoint volume and acid concentration, indicating accurate quantification.

Conclusions:

• The developed miniaturized titration system using agarose beads is a viable and efficient method for acid concentration determination.
• This approach overcomes challenges associated with mixing and dilution in laminar flow conditions.
• The method demonstrates high accuracy and linearity, suitable for practical analytical applications.