Storage condition

Nominal concentration (ng/mL)

Measured concentration (ng/mL)

Recovery (%)

Short-term stability (6 h in plasma)

30

18,749^*

108.53

600

-

-

960

582,694^*

89.00

Autosampler stability after 65 h

30

29.53

99.53

600

-

-

960

918.43

98.37

Freeze-thaw cycles (N = 5)

30

31.70

105.67

600

602.13

100.36

960

1039.94

108.33

Long term stability (198 day, −80˚C)

30

29.80

99.34

600

582.82

97.14

960

945.21

98.46