In a simple experiment, I measured the pH of Tween 80 solutions and observed that the pH decreased. investigation results :
3 ppm tween80 = 8.43
6 ppm tween80 = 8.24
12 ppm tween80 = 7.51
15 ppm tween80 = 7.31
1780 ppm tween80 = 4.22
3560 ppm tween80 = 4.05
7120 ppm tween80 = 4.09
Solutions were made in distilled water. It seems that pH increased first and then increased with increasing concentration.
Did you use DI water or really distilled water? The ion exchangers used for DI water may leave minor residuals, so check the pH of that.
Regarding the decreasing pH: that seems to be the expectation, German Wikipedia says a 5% watery solution should have a pH in the range 5-7. The statement is referencing this article (which I haven't checked for now because I don't have access to it from here):
https://www.sciencedirect.com/science/article/abs/pii/S0022354916317774?via%3Dihub
Based on the information you provided, it appears that the addition of Tween 80 to a solution in distilled water initially increased the pH, and then decreased it as the concentration of Tween 80 increased.
Tween 80, also known as polysorbate 80, is a surfactant commonly used in various industries, including food, cosmetics, and pharmaceuticals. It is known to be relatively neutral and does not have a significant effect on pH in most cases.
However, it's important to note that pH measurements can be influenced by various factors, such as the presence of impurities or interactions with other components in the solution. It's possible that the observed decrease in pH with increasing Tween 80 concentration is due to such factors rather than a direct effect of Tween 80 on pH.
To determine the exact cause of the pH changes in your experiment, it would be necessary to investigate other factors that may have influenced the measurements, such as impurities in the Tween 80 solution or potential reactions between Tween 80 and other components in the solution.
It's also worth considering that pH measurements can be affected by experimental errors or limitations of the pH measurement method used. Therefore, it would be beneficial to ensure accurate and precise pH measurements using calibrated instruments and appropriate techniques.
In summary, based on the information provided, Tween 80 itself is not expected to directly decrease the pH of a solution. Further investigation is necessary to understand the factors contributing to the observed pH changes in your experiment.
@ Arash, it is surprising. Actually tween 80 is a surfactant and its pH value ranges between 5 and 7. It is a organic solvent, therefore, hardly it can alter the pH but really not expected to decrease the pH so much. I agree with Dr. Sergio, please check it further for final conclusion.
Tween 80 is an ester formed from the reaction of polyethoxylated sorbitan and oleic acid. Though the reaction product is neutral, a small amount of sulfuric acid is sometimes used to catalyze esterification reactions such as the one that forms Tween 80. Is it possible that Tween 80 contains a small amount of residual sulfuric acid from the reaction that produces it? This would account for the decreasing pH as you increase the concentration of Tween 80.
- Badges
- Science method