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. Author manuscript; available in PMC: 2011 Nov 15.
Published in final edited form as: J Chromatogr B Analyt Technol Biomed Life Sci. 2010 Sep 29;878(30):3187–3192. doi: 10.1016/j.jchromb.2010.09.017

Table 2.

Freeze-thaw and autosampler stability

Freeze-thaw stability Autosampler stability
Calculated QC concentration, ng/mL (percent with respect to cycle zero concentration) Calculated QC concentration, ng/mL (percent with respect to zero hr concentration)
Nominal concentration (ng/mL) Fresh After 1 Cycle* After 2 Cycles* After 3 Cycles* Zero hr 24th hr % Change
7.5 7.1 (100) 7.8 (109) 7.5 (105) 7.7 (108) 8.0 7.8 (97.5) −2.5
150 135.1 (100) 146.1 (108) 147.2 (109) 145.4 (108) 152.2 146.1 (99.2) −0.8
1500 1398.9 (100) 1519.9 (109) 1521.4 (109) 1522.9 (109) 1565.1 1519.9 (99.0) 1.0
*

number of freeze-thaw cycles