Table 2.

Matrix Effects on Detection of Estrogen Metabolites. We compared the peak height of EMs spiked at given concentrations (250, 1000 or 6400 pg/mL) into charcoal stripped human urine (CSHU) and in neat LC solvent A (S). Matrix effects were observed based on the recovery of signal (%) in urine as compared with LC Solvent A. For most analytes, significant matrix effects (> 20%) were not observed. Estrogen metabolite 17-epiE3 showed lower signal in urine samples, indicating significant signal suppression. Interference was also very low, as few values for EM signal in CSHU exceeded 100% of the values observed for EMs in solvent.

Metabolite	Average Recovery in CSHU vs. Neat Solvent (%)
	250 pg/mL	1,000 pg/mL	6,400 pg/mL
E3	86	93	92
E1	87	94	92
2-OHE1	89	94	93
16-ketoE2	98	73	102
4-OHE1	100	113	122
16α-OHE1	94	98	92
2-MeOE1	102	109	98
4-MeOE2	86	93	91
E2	89	94	93
16-epiE3	93	91	95
17-epiE3*	47	51	61
4-MeOE1	87	94	94
2-OHE2	108	110	97
3-MeOE1	88	93	91
2-MeOE2	89	93	93

^*No standard was available for 17-epiE3, so the closest analogue, D₂-16-epiE3, was used.