Day

RK level (mg/mL)

Recovery added (0.25 mg)

Day 1

Day 2

Day 3

Day 4

Day 5

1.12

1.13

1.16

1.22

1.28

82.9

81.2

79.6

88.8

86.9

Average ± S.D.(R.S.D.)

1.18 ± 0.07 (7.4%, n = 5)

83.9% ± 3.9% (4.6%, n = 5)