Nonaqueous acid-base titrations – Common mistakes and how to avoid them
Jul 12, 2021
Article
Nonaqueous acid-base titrations are widely used in several industries, including the petrochemical and pharmaceutical sectors. Whether you are determining the acid or base number (AN or BN) in oils or fats, titrating substances that are insoluble in water, or quantifying products with different strengths of acidity or alkalinity separately, nonaqueous acid-base titration is the method of choice.
If you already have some experience performing nonaqueous acid-base titrations, you may remember that there are several challenges to overcome in comparison to aqueous acid-base titrations.
In this blog post, I would like to cover some of the most typical issues that could pop up during nonaqueous acid-base titrations and discuss how to best avoid them. An important point to note is that there is no single solution regarding how to perform any nonaqueous acid-base titration correctly. The right procedure depends highly on the solvent and titrant used.
To jump directly to a specific topic, click on the corresponding link below:
- What is a nonaqueous acid-base titration?
- Electrostatic effects
- Blocked diaphragm
- Choice of electrolyte and storage solution
- Checking the electrode according to ASTM D664
- Proper rinsing and cleaning
- Conditioning the glass membrane
- Maintenance of burets
- Thermometric titration as an alternative
- Summary
What is a nonaqueous acid-base titration?
Before discussing nonaqueous titrations, first let’s talk a little bit about aqueous acid-base titrations.
Here, a sample is dissolved in water, and depending of the nature of the sample (whether it is acidic or basic) a titration is performed either using aqueous base or aqueous acid as titrant. For indication, a glass pH electrode is used.
However, sometimes due to the nature of the sample, aqueous titration is not possible. Nonaqueous acid-base titration is used when:
- the substance of interest is not soluble in water
- samples are fats or oils
- components of mixtures of acids or bases have to be determined separately by titration