Table 4.

Stability of RES in blood and tissue samples.

Analyte	Added concentration	Long-term (−20 °C), Re (%)	Short-term (20 °C), Re (%)	Freeze-thaw, Re (%)	Post-preparation (20 °C), Re (%)
Plasma (ng/mL)	20	−3.56	−4.66	−3.46	−6.45
	500	−2.67	−6.35	−3.56	−1.45
	1000	−4.26	−5.45	−8.35	−2.66
Heart (ng/g)	50	−2.36	−1.45	−11.36	−1.45
	1000	−1.37	−6.35	−2.45	−3.67
	2000	−4.75	−5.83	−6.37	−4.35
Liver (ng/g)	50	−6.35	−9.34	−7.36	−5.36
	1000	−8.36	−3.53	−2.17	−7.35
	2000	−2.74	−10.65	−5.34	−6.72
Spleen (ng/g)	50	−3.54	−6.34	−2.57	−3.62
	1000	−6.37	−2.46	−2.56	−0.46
	2000	−6.26	−0.64	−4.76	−7.75
Lung (ng/g)	50	−4.74	−4.75	−6.34	−0.36
	1000	−8.45	−3.69	−4.76	−2.57
	2000	−7.26	−2.58	−5.34	−2.68
Kidney (ng/g)	50	−2.47	−2.57	−6.55	−3.76
	1000	−4.78	−8.36	−3.57	−6.36
	2000	−8.46	−6.36	−7.45	−5.34
Brain (ng/g)	50	−9.47	−3.54	−7.64	−3.71
	1000	−2.45	−2.65	−7.35	−7.49
	2000	−1.45	−3.57	−3.45	−2.75