Hi everyone,
I'm a PhD student facing a persistent issue in the sample preparation step for microplastic analysis.
I'm digesting marine fish tissues (gills, gastrointestinal tract, and muscle) with 10% KOH to isolate microplastics. The challenge arises during vacuum filtration of these digested samples: the formation of excessive and persistent foam prevents liquid from passing through the filter, making filtration extremely slow or impossible.
I've already tried pre-wetting the filtration system with absolute ethanol and neutralizing the pH of the digested samples with citric acid before filtration. So far, with no success.
Has anyone in the community encountered this foaming issue with KOH-digested tissue samples? What strategies have worked for you?
Thanks a lot for help!
You might be able to add a defoamer to your system.
the reason you get foam is that the KOH digest hydrolyzes (saponifies) the triglyceride oils in your sample to make potassium fatty acid salts - soap.
water based defoamers with long chain alcohols might be a good choice, for example.
Apply 100% ethanol to the samples to take away the saponification
Thank you for the valuable suggestions and explanations!
Regarding the suggestion about 100% ethanol post-digestion: I tried it, but unfortunately, a viscous jelly-like precipitate formed on the filters, completely impeding filtration.
I appreciate the explanation about fat saponification causing the foam. I'm not familiar with specific anti-foaming agents, but I will certainly look into those options. Regarding their application, would it be best to add them directly to the digested samples, or should I perform a preliminary filtration step first in my system?
You can use tween 20. It has been used in many studies and does not alter the shape and color. Read this paper for more information Article Improved methodology for microplastic extraction from gastro...
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