When performing a chromatogram of the same sample of water stored for months in plastic or glass bottles there are appreciable differences? What is due?
Impurities in plastic may give some extra peaks but i dont think the difference if you stored in glass. still, if there is a microbial growth, you can see the changes in chromatogram
Difference is due to the presence of leachables. Glass will not contain leachables. Plastic bottles can contain leachables. Depends on the plastic, but some may contain bisphenol A or phthalates.
Article Organic Extractables from Packaging Materials: Chromatograph...
However, most plastic bottles would be made from PET, which should not contain either compound. However, new evidence suggest that phthalates (endocrine disruptors) may be leaching from PET bottles due to the presence of recycled PET inner layers. Or some other mechanism. Work is ongoing in the area.
Article Polyethylene Terephthalate May Yield Endocrine Disruptors
Felipe, I would first find the type of plastic used to make the bottle. Look for the recycle number in a triangle on the label or on the actual bottle. The number will correspond to a plastic. From here you can narrow down the potential identity of the leachable.
Inorganic glass bottles can have very different compositions. If the bottle is a soda lime silicate (most common type of glass bottle), it will leach sodium and maybe some potassium (depends on composition) into the water. It also depends on the size of the bottle and the amount of water (the volume to surface ratio).
If the bottle is a borosilicate, it will probable leach far less sodium. Again it depends on things like the prior usage of the bottle (is it new or has it been used many times?), the specific type of borosilicate (pharmaceutical bottles will be more leach resistant), the thermal history of the bottle itself, etc.
In other words, there is no simple answer with the information you provide. And, of course, it depends on the sensitivity of your analysis.
I don't know anything about plastics, but I'll bet they also leach something.
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