Final answer:
Bilirubin specimens require plasma samples collected into tubes containing K2EDTA and centrifuged to obtain plasma. Urine samples do not require any special preparation.
Step-by-step explanation:
Bilirubin specimens require plasma samples collected into tubes containing K2EDTA and centrifuged to obtain plasma. These plasma samples are then quenched with methanol immediately before analysis. There is no special preparation required for urine samples before analysis.