. Author manuscript; available in PMC: 2009 Dec 15.

Published in final edited form as: J Chromatogr B Analyt Technol Biomed Life Sci. 2008 Nov 6;876(2):219–224. doi: 10.1016/j.jchromb.2008.10.046

Table 4.

Stability of quality control samples (n = 5)

Nominal concentration (ng/mL)	Measured mean concentration (ng/mL) ± S.D	CV(%)	Mean accuracy (%)
Three freeze/thaw cycles (−20 °C)
20	18.38 ± 0.63	3.45	91.96
500	577 ± 27.03	4.69	115.50
2000	2202 ± 87.01	3.95	108.75
Autosampler, 4 °C, 72 h
20	20.40 ± 1.26	6.45	102.12
500	493 ± 38.70	7.85	98.56
2000	1960 ± 175.78	8.97	98.14
Ambient 24 h
20	17.4 ± 0.83	4.80	87.00
500	508.75 ± 11.98	2.36	101.93
2000	1840 ± 85.44	4.64	92.10
Storage stability (−20 °C; 1 month)
20	18.66 ± 0.94	5.28	93.28
500	464.80 ± 20.58	4.43	92.90
2000	1874 ± 64.27	3.43	93.70