Bitan:Calculating specific activity of hot CTP after calibration date

Calculating the specific activity of α-32P-CTP after the calibration date

CTP used is from Perkin Elmer CTP, α-32P- 3000 Ci/mmol, 10 mCi/ml , 250 µCi. Reference date for this lot was 11/21/09. The activity calculated for this lot on 11/27/09 is as follows:

This is CTP lot was 6 days old. The activity of α-32P-CTP, lot RSO0117175 was 0.748 of total activity on 11/27/09 based on the decay chart below. According to this formula, the total activity was calculated to be 2447 Ci/mmol on 11/27/09:

where SAtheo.=9120 for the theoretical specific activity of carrier-free 32P; SAcal.=specific activity after the calibration date; and DF is the fraction of current radioactivity that will remain on the calibration date from the Decay Chart. So in this case

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After the reference date, the total activity of the fresh hot CTP was 250 μCi in 25 μl, and the concentration was 10 μCi/μl (10 mCi/ml). But now, it is 187 μCi because 0.748×250=187. If 4 μl was used for in vitro transcription reaction, the total amount used would be for each reaction.