advantages of the solid-phase ria method are as follows : ( 1 ) 0.05 ml of plasma or serum was sufficient for determination of plasma cortisol concentrations , ( 2 ) no other solvents or solutions for the extraction or purification were required , ( 3 ) the procedure was simple and readily facilitated , and ( 4 ) the concentration of cortisol in heparin-plasma was somewhat higher than that in serum or edta-plasma , but there was no statistical difference .
C0229671
serum
C0032105
plasma