Because a plastic bottle can contaminate the sample; and a glass bottle is fragile.
mechanicals
Chemical (bleach mixed in) Bacterial (salmonella) Physical (a metal shaving)
No. Enzymes are biological and thus are related to living things; metals are not biological.
Metal in the transmission pan indicates a problem with the transmission. The most likely cause is gears grinding against one another, shaving off small bits of metal as they do so.
It prevented thieves from shaving off precious metal from around the edges of coins.
Hassium is a synthetic element that is a metal. It is highly radioactive and has no known biological functions.
Drill bits will sometimes become magnetized from use, but not as a deliberate thing. It would cause the shaving from the drilling of metal to cling to the bit. You want the shaving to get out of the way so that you can judge how the drilling is progressing.
Within USDA FSIS (Food Safety and Inspection Service), there are three categories of hazards that must be addressed within the regulated establishment's HACCP plan - chemical (cleaners, sanitizers, preservatives, etc.), biological (E. coli, Salmonella, Listeria monocytogenes, etc.), and mechanical (foreign particles, wood chips, metal flakes, etc.).
Metal shaving in a cylinder on a vehicle is a sign of a major problem that could lead to complete engine malfunction. The solution is to tear the motor apart and rebuild or replace defective parts.
That will vary depending on the type of contaminate. Some contaminates cannot be removed with chemicals (e.g. metal particles - these need to be removed with a filter).
Iron is the most abundant transition metal. It is found in large quantities in the Earth's crust and plays a crucial role in many biological processes.