I know that you can measure hydroxyproline from tissues which have a greater amount of collagen than cells. However I need to measure hydroxyproline from cells grown from a 12 well plate well.
Also, I noticed that standards when dried at 60 C show a more shallow slope than standards not dried in the oven at 60 C.
The Sigma kit's protocol calls for drying samples at 60 C or an evaporator before doing the assay. If the 60 C oven affects the standards it probably affects the samples as well.