Table 2: Summary of stability of morphine and codeine under various storage conditions .

CompoundConditionConcentration (ng/mL)RSDRE
Added(%)(%)

MorphineThree freeze–thaw cycles502.5−10.1
2001.4−8.9
16004.3−12.5
Autosampler ambient 12 h502.1−10.5
2001.3−6.2
16003.5−9.2

CodeineThree freeze–thaw cycles503.2 −8.9
2003.3 −11.2
16003.0 −14.1
Autosampler ambient 12 h503.3 −11.1
2003.2 −12.9
16003.3 −14.4