A Simple and Rapid LC-MS/MS Method for Quantification of Total Daidzein, Genistein, and Equol in Human Urine

Table 3

Validation data for each analyte in human urine.

Compound	R^2(a) (n = 10)	Slope^(b) (n = 10)	Precision, intraday (%)^(c)	Precision, interday (%)^(d)	Precision in spiked sample (n = 10) (intraday), RSD (%)			Precision in spiked sample (n = 10) (interday), RSD (%)			Accuracy (%)			LOD (ng/ml)	LOQ (ng/ml)
					L	M	H	L	M	H	L	M	H
Daidzein	0.995	2.763	5.9	8.15	9.0	6.37	5.7	19	14.8	11	>100	>90	>90	1	3
Genistein	0.996	0.009	7.2	7.3	4.73	4.1	2.80	17.8	14.1	8.9	>100	>90	>90	1	3
Equol	0.997	3.189			9.24	5.33	3.33	19.1	14.8	8.5	>100	>90	>90	2	6

^(a)R² for calibration curve (a measure of goodness of fit of the least squares linear regression); values are mean of 10 calibration curves. ^(b)Values are mean of 10 calibration curves; units are peak area ratio (μg/ml)⁻¹. ^(c)Precision (determined in an authentic volunteer sample, n = 6 replicate analyses); value is relative standard deviation (RSD). ^(d)Precision (determined in an authentic volunteer sample, n = 10 analyses on different days); value is RSD. L: low-concentration quality control sample; M: medium-concentration quality control sample; H: high-concentration quality control sample; LOD: limit of detection; LOQ: limit of quantification.