15°C | −20°C | −70°C | |||||||
---|---|---|---|---|---|---|---|---|---|
Days | 1 | 1 | 4 | 8 | 31 | 1 | 4 | 8 | 31 |
E1 | 100 | 99 | 94 | 99 | 109 | 103 | 98 | 104 | 109 |
17β-E2 | 102 | 101 | 99 | 101 | 103 | 100 | 96 | 100 | 105 |
17α-E2 | 122 | 132 | 115 | 111 | 115 | 112 | 92 | 103 | 117 |
E3 | 100 | 97 | 95 | 99 | 102 | 98 | 96 | 101 | 97 |
4OH-E2 | 100 | 72 | 38 | 45 | 38 | 71 | 36 | 46 | 30 |
2Me-E2 | 100 | 25 | 79 | 22 | 28 | 22 | 75 | 13 | 17 |
4Me-E2 | 100 | 66 | 115 | 55 | 97 | 72 | 109 | 45 | 75 |
Stability was assessed in standard extracts following storage at different temperatures. Storage times were 1, 4, 8, and 31 d, and temperatures were 15°C (autosampler), −20°C, and −70°C. Values were calculated as the percentage to the area ratio measured at time 0. Time zero was defined as the time point when injection into the LC-MS/MS occurs immediately following derivatization.