Ferulic acidAdded (ng/ml) Stability Mean (ng/ml) SD RSD(%) RE (%) 5 5.17 0.44 8.4 3.4 500 518.49 12.13 2.3 3.7 3000 2789.28 120.79 4.3 -7.0

Ferulic acid standard solution at different concentrations of 5, 500 and 3,000 ng/ ml in rat plasma was prepared. After three freeze-thaw cycles, the samples were injected into UPLC-MS/MS to determine the stability of ferulic acid. Mean of the concentration (ng/ml) of ferulic acid in rat plasma, SD, RSD (%) and RE (%) was calculated, n = 3.

Table 5: Stability of the analysis of ferulic acid after freeze-thaw cycles.