What I want to do
Understand why used Kitagawa tubes are turning pink in our fridge. We've been storing them in there for a while, and they've been stable-- i.e. if I put a tube in there it has the same reading the next day. Then, starting over the past two weeks they've been getting pinker (exposed) in the fridge.
My attempt and results
Of recent additions to the fridge, the biggest and funkiest is definitely this half-gallon of kimchi I put there. I really like kimchi. You can definitely smell it when you open the fridge.
Kimchi is actively decomposing, My suspicion is that these aromatic decomposition gasses are affecting the tubes. Kitagawa lists these false-positives and cofounding gasses:
Nitrogen dioxide is an intermediate component in anaerobic metabolism, which is likely to be occurring in the kimchi. Acetaldehyde may also be generated by partial metabolization of alcohol, although the lacto-fermentation of kimchi shouldn't generate that, I don't think. Acetaldehyde is also carcenogenic, but at much higher concentrations than formaldehyde.
Questions and next steps
What else do you think it is?
Why I'm interested
confounding factors to formaldehyde testing are important to recognize and potentially account for with other tests.