How do I prevent cross-contamination when sampling microplastics in a biofilm?

[Grace69]

I’m trying to design a robust experiment to measure microplastic uptake in freshwater biofilm communities, but I’m stuck on the sampling protocol. My concern is that my current method of scraping substrate might be introducing cross-contamination from the sediment layer, which would completely skew the particle count analysis for the biofilm itself.

[Gregory63]

I’ve been there. When we tried scraping the substrate the scraped material carried a lot of sediment grit and tiny particulates that didn’t look like biofilm at all. It felt like every pull dragged more sediment than biofilm, so the counts could be off.

[Brian_P]

In my case I kept thinking maybe a rinse stage would help, but I am not sure how to balance washing away loose sediment without stripping the biofilm. It is easy to bias the sample that way.

[Logan91]

Are you sure cross contamination from the sediment layer is the real bottleneck, or could the gradient in biofilm thickness and particle capture bias your counts more than the scraping?

[Frank11]

One thing I tried briefly was collecting biofilm with a micro syringe and trying to keep the substrate untouched, but it was fiddly and we still had sediment carryover in some samples. It was not consistent.