The human blood samples were collected in Vacutainer® tubes containing K2EDTA. After obtaining the blood sample, collection tubes were slowly inverted 8–10 times to mix the blood and anticoagulant thoroughly. Then 1.5 mL of blood sample was transferred to a labeled sample tube which contained 4.5 mL of 0.5 N perchloric acid solutions. The acidified human whole blood samples were stored at –70 °C until analysis.