Extinction coefficients are a prediction of each oligo’s molar absorbance and the standard method to calculate concentration. To estimate the extinction coefficient of modified oligonucleotides, we use the following equation: ε260 = [(Sum of ε260 for all bases) + (ε260 for all modifications)] x 0.9, to adjust for hyperchromicity. Individual extinction coefficients for each modification are available under the Technical Specs tabs on our Oligo Modifications webpages. The extinction coefficient found on the Certificate of Analysis for a custom oligo includes all dye and other modifications in the presented value. Simply use this value and measure the OD at 260 nm to calculate oligo concentration according to Beer’s Law. 

If you need additional information, please contact our Technical Support team.