Potassium hydroxide: suitable for isolating plastic particles from marine organisms?

Published on
February 13, 2017

Does potassium hydroxide, a substance used to filter organic material from stomachs of marine animals, impact different kinds of plastic in the same way? A new article sheds light on this question.


In January 2016, the EU Joint Program Initiative Oceans (JPIO JPI OCEANS) launched a number of international research projects on marine microplastics. One of these is the PLASTOX project, which aims to study the direct and indirect ecotoxicological impacts of microplastics on marine organisms. In the Netherlands, ALW-NWO granted a PLASTOX PhD position to Wageningen Marine Research in Den Helder.

This PhD position was given to Suse Kühn, due to her large experience with plastic work on fulmars and other marine organisms. Suse and co-authors have now published the first scientific paper of the PLASTOX group, and presented it during the annual PLASTOX consortium meeting on the 1st of February 2017 in Marseille, France.

Group members of the PLASTOX consortium meeting in Marseille, France (February 2017)
Group members of the PLASTOX consortium meeting in Marseille, France (February 2017)

Potassium hydroxide

The paper examines the suitability of potassium hydroxide (KOH) to isolate plastic particles from marine organisms. KOH is a solution that dissolves organic material and can be used to find plastic inside of stomachs of small organisms such, as fish, more easily.

However, it was unclear whether the KOH would have an impact on different plastic types, which could create bias when studying the abundance of ingested plastic in organisms. Therefore, a series of different plastic types and shapes, both pristine and collected from beaches, was exposed to KOH. Additionally, plastics were exposed to seabird stomach fluids, to evaluate whether enzymatic or acidic influences had an influence on plastics treated with KOH solutions.


The results show that most plastics can stand a treatment with KOH with the exception of some bioplastics and cellulose acetate, which is used in cigarette filters. Therefore, where needed, the KOH method will be used for future studies on the ingestion of plastics by marine organisms.

Kühn, S., Van Werven, B., Van Oyen, A., Meijboom, A., Bravo Rebolledo, E.L. & Van Franeker, J.A.  (2017). The use of potassium hydroxide (KOH) solution as a suitable approach to isolate plastics ingested by marine organisms,.  Marine Pollution Bulletin 115, 86-90. (open access).