Matrix Concentrations tested Estrone Recovery %   RSD (%) Estradiol Recovery %   RSD (%) 17a-ethinylestradiol Recovery %   RSD (%) Estriol Recovery %   RSD (%) Distilled Water sample    20 µg L-1 110          0.3 115          0.42 116            0.65 101          1.47    10 µg L-1 110          0.06 111          0.79 120           0.72 97            0.05    1 µg L-1 115          1.02 106          0.06 110            1.32 85            0.10   Correlation coefficients 0.9977 0.9993 0.9993 0.9998

Table 3: Recovery data for target estrogens in distilled water after SPE at different initial concentrations (n=3).