I obtained a oligo from Trilink 47 bp in length with the presence of a random fragment that was 10bp. Scale ordered: 0.2umole Extinction coefficient: 457.1 units/umol Od= 63.5 MW= 14334.9 g/mole I calculated the molarity as umol= OD/extinction coefficieint = 63.5/457.1= 0.138umol To make 1mM of the oligo I added 138ul of water to the mixture. Now total MW= 0.138 * 14334.9 = 1978.2ug But as there are 138 ul each ul should have a concentration of 14.339 ug but each ul of my sample had 1 ug concentration. Is there an error to my calculations? -Anjali

Dear Anjali,

Thank you for your inquiry. A final concentration of 1 uM means you have 1 μmole or 14.34 ug per L. Concentrations should be confirmed with OD readings of the final solution. Please remember, the extinction coefficient and molecular weight reported is calculated average and the final values of a randomer oligonucleotide may vary.

We’re happy to discuss how to measure the concentration of you solution. Please email us to discuss measuring the absorbance.

Best regards,