For the measurements the blood plasma (300 ll) was dissolved
in 1 ml of total volume using PBS (phosphate buffer, 5 mmol/L, pH
7.4, plus NaCl 0.9%). Before each measure the potential of the PBS
solution was recorded. The redox potential (DE), as presented here,
is the difference between the sample potential (Es) and the buffer
potential (Eb): DE = Es Eb. All measurements were made 120 s
after sample addition, the time required to stabilize the electrodes.