Content of ACN/% RRTc sd(n=3) 40 11.528 11.065 1.042 1.138 0.018 50 4.581 4.451 1.029 1.087 0.021 60 2.583 2.521 1.025 1.058 0.009 70 1.787 1.757 1.017 1.008 0.041 90 1.219 1.201 1.015 0.928 0.034

asample: progesterone; bIS: Internal Standard, D9-progesterone; cRRT: Relative Retention Time

Table 2: Retention time and the relative response of progesterone and D9-progesterone in different mobile phase.