Table 4.

Extraction efficiency, linearity and sensitivity of assay in rat tissues

Sample		Tissue concentration	Linear range (nM)	In vivo sample range (nM)	Extraction efficiency (%)	LOQ (nM)	Sensitivity (pg)
Plasma	DXR	20% (v/v)	0.343–10,000	0–5000	87.2	0.343	1.87
	DXR-ol	20% (v/v)	0.945–10,000	0–2000	ND	1.89	10.3
Brain/tumor	DXR	5% (w/v)#	0.125–1000	0.6–126	91.4	0.25	1.36
	DXR-ol	5% (w/v)#	0.500–1000	0.4–92	ND	0.5	2.73
Liver	DXR	0.5% (w/v)	0.686–1000	43–240	88.9	2.06	11.2
	DXR-ol	0.5% (w/v)	2.06–1000	4–18	ND	2.1	11.2
Spleen	DXR	1% (w/v)	2.06–1000	91–846	91.8	2.06	11.2
	DXR-ol	1% (w/v)	2.06–1000	18–246	ND	2.1	11.2
Heart	DXR	2.5% (w/v)	1.37–1000	60–680	112	2.06	11.2
	DXR-ol	2.5% (w/v)	2.06–1000	11–55	ND	2.1	11.2
Lung	DXR	2.5% (w/v)	2.06–1000	267–931	84.2	2.5	13.6
	DXR-ol	2.5% (w/v)	2.06–1000	4–42	ND	2.1	11.2

Standard solutions of DXR or DXR-ol were prepared in blank plasma or tissue homogenates at known concentrations ((v/v) or (w/v)), extracted, and analyzed by LC–MS/MS. The extraction efficiency, linearity, and sensitivity of the method were determined. The in vivo sample range was determined after analysis of plasma and tissue samples from rats (n ≥ 12) treated intravenously with 5.67 mg/kg SSL–DXR. LOQ: limit of quantification; ND: not determined;

^#concentration of brain tumor homogenate ranged from 3–7% (w/v).