Determining ENU concentration by Spectrophotometry

Why bother? Lore has it that the Sigma Isopac of ENU, which contain approximately 1 gm, can vary anywhere from 0.6 - 1.5 gm.

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Method:

1. Dissolve 1 gm Isopac ENU in 85 ml ENU dilution buffer (see below).
   
   
2. Dilute 100 ?l ENU solution to 2 ml with ENU dilution buffer (i.e. 1:20 dilution)
   
   
3. Determine OD₃₉₈ using a disposable plastic cuvette.
   
   
4. 1 mg/ml solution of ENU gives OD₃₉₈ =0.72.
   Therefore, x gm ENU = (OD₃₉₈)(20)/(0.72)(0.085L)
   or
   x gm ENU = (OD₃₉₈)(2.36)
   
   
5. To make a solution of [ENU]_final = 3 mM
   (y L_final)(0.003 M ENU) = x gm ENU/117.3 gm/mol ENU
   or
   y L_final = x gm ENU/0.352
   or
   y L_final = (OD₃₉₈)(6.71)

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ENU Dilution Buffer
0.03% Instant Ocean
10mM NaPO₄, pH6.5

Reference:

Justice et al., (2000). Effects of ENU dosage on mouse strains. Mam. Gen. 11, 484-488