Spiked Found (mean ± SD, μg/mL) (μg/mL) Freeze–thaw for three cycles Room temperature for 8 h Autosampler for 24h 0.5 0.43 ± 0.01 0.56 ± 0.10 0.54 ± 0.08 5 5.22 ± 0.07 4.93 ± 0.18 4.91 ± 0.12 40 39.39 ± 1.39 39.28 ± 1.40 40.37 ± 1.40

Table 3: Stability test of STS during the storing and preparation procedures (n=5).