2.6. Samples
The sample manipulation was approved by the ethic committee of the Federal University of Alfenas (process CAAE:19377213.1.0000.5142). The blood samples were collected by venous pulsing, coagulated and centrifuged during 15 min at 100g, in order to separate the serum. Then, the samples were diluted at the proportion of 1:1 v/v with a phosphate buffer 0.01 mol L1 (pH¼5.7), and directly analyzed in the system.