How do I quantitate oligonucleotides by spectrophotometer?

Protocol for the Quantitation of Oligonucleotides by Spectrophotometer:

1. Add an aliquot of the resuspended oligonucleotide to a final volume of 1000 µl of water or appropriate diluent.
2. Vortex or pipette up and down for 15 seconds.
3. Read the absorbance of this dilution at 260 nm (A260).
4. Use the formula below to calculate the molar concentration (use the nmol/ OD260 from the Certificate of Analysis in your calculation) of oligonucleotide in your stock solution.
Concentration in nmol/ml = A260 × nmol per OD × dilution factor*
(* the dilution factor is determined by 1000/amount of resuspended oligo added for the dilution, i.e, if you added 50 µl of resuspended oligo to 950 µl of water to read the absorbance, you dilution factor would be 1000/50 = 20)

If you have to calculate molar concentration and the nmol/ OD260 value is not readily available, the following formula will also work.

Concentration in nmol/ml = A260 × dilution factor × 10^6 / Molar Extinction Coefficient

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