Stability Spiked conc. (pg/ml) Mean (± SD) obtained concentration % Change (Stability)
Comparison samples (pg/ml) Stability samples (pg/ml)
Bench topa 27956.635 27428.770 (± 71.101) 27557.790 (± 74.193) 0.47
14537.450 13708.226 (± 125.746) 13916.554 (± 53.782) 1.52
290.749 279.777 (± 4.203) 284.292 (± 2.066) 1.61
Process stabilityb 27956.635 27466.251 (± 107.836) 27348.265 (± 322.401) –0.43
14537.450 14430.853 (± 107.114) 14353.333 (± 131.016) –0.54
290.749 291.135 (± 3.740) 289.277 (± 7.848) –0.64
Freeze/thawc 27956.635 27684.246 (± 72.812) 27549.256 (± 132.294) –0.49
14537.450 13914.170 (± 126.952) 13768.270 (± 95.724) –1.05
290.749 272.259 (± 4.331) 275.954 (± 4.053) 1.36
Freeze/thawd 27956.635 27684.246 (± 72.812) 27556.702 (± 182.816) –0.46
14537.450 13914.170 (± 126.952) 13742.464 (± 74.795) –1.23
290.749 272.259 (± 4.331) 275.627 (± 3.827) 1.24
Long terme 27956.635 29103.028 (± 276.083) 29116.039 (± 376.954) 0.04
14537.450 15159.266 (± 105.244) 15144.490 (± 147.049) –0.10
290.749 293.156 (± 12.237) 292.720 (± 12.506) –0.15
Long termf 27956.635 29103.028 (± 276.083) 29266.360 (± 685.306) 0.56
14537.450 15159.266 (± 105.244) 15145.190 (± 94.743) –0.09
290.749 293.156 (± 12.237) 293.062  (± 10.547) –0.03
Long termg 27956.635 29082.193 (± 323.626) 28937.989 (± 291.306) –0.50
14537.450 15091.547 (± 76.126) 15036.159 (± 135.769) –0.37
290.749 307.782 (± 13.278) 306.090  (± 13.228) –0.55
Long termh 27956.635 29082.193 (± 323.626) 29009.723 (± 549.216) –0.25
14537.450 15091.547 (± 76.126) 15075.167 (± 94.549) –0.11
290.749 307.782 (± 13.278) 310.764  (± 13.021) 0.97
* - % Change – Determined by calculating the percentage change of mean of stability QC concentration against mean of comparison QC concentrations
aAfter 6 hours at room temperature
bAfter 75 hours in autosampler at 10°C
cAfter five freeze/thaw cycles at –30°C
dAfter five freeze/thaw cycles at –75°C
eLong term matrix stability at –30°C for 72 days
fLong term matrix stability at –75°C for 72 days
gLong term matrix stability in presence of ethinyl estradiol at –30°C for 73 days
hLong term matrix stability in presence of ethinyl estradiol at –75°C for 73 days
Table 3: Stability results for levonorgestrel (n=6).
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