Monovette in theory could cause contamination with EDTA if that tube is used first because the lower part of the needle is in the bottle and so can come into contact with blood that has mixed with EDTA in the tube.
I was always told to take those as last sample
---
Elwood: "It's 106 miles to Chicago, we've got a full tank of gas, half a pack of cigarettes, it's dark and we're wearing sunglasses."
Jake:" Hit it."