TABLE A4.

Limits of detection (LOD) and resolution (R_s) of the atropisomers of PCB 136 and its hydroxylated metabolites in rat liver slices.

Parameter	PCB 136 (ng)		5-OH-PCB 136 (ng)		4-OH-PCB 136 (ng)
	(−)	(+)	E(1)	E(2)	E(1)	E(2)
LOD on Chirasil-Dex column	39.8 (n = 3)	50.7 (n = 3)	ND		NA
LOD on Cyclosil-B column	NA		NA		5.3 (n=3)	5.1 (n=3)
Rs	0.73		0.61		0.74

The LOD was calculated from blank samples as $\mathit{LOD}=\overline{x_b}+k·s_b$, where $\overline{x_b}$ is mean of samples, k is Student’s t-value for n−1 degrees of freedom at 99% confidence level, and s_b is standard deviation of the blank measures (Kania-Korwel et al., 2007). The R_s was calculated using the formula R_s = (t_R2 − t_R1)/0.5(BW₁ + BW₂), where t_R2 and t_R1 are the retention times of the first and second eluting enantiomer, and BW₁ and BW₂ are the baseline width of the first and second eluting enantiomer (Kania-Korwel et al., 2008b). NA, not applicable. ND, not determined. A comparable study determined the LOD for E₍₁₎- and E₍₂₎-5-OH-PCB 136 to be 9.9 and 16.8 ng, respectively (Wu et al., 2011).