Table 5.

Stability of estrogen DMIS derivatives

	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.