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