How one can quantify the oligonucleotides for 10 - 100pM range, i had used nanodrop to quantify but ended up with the result same as blank. The oligo's had dispensed in nuclease free water.
You need OD reading over 0.1 or better over 0.2 for using nanodrop!
If you have an oligo of 25 bases, extinction coefficient will be from about 176000(all C) to 380000(all A). For 100pM concentration, OD is from 176000x100x10(-12) to 380000x100x10(-12), way to low!
You can measure OD of higher concentration and then do dilution, consider the dilution is good enough!
Or
You should use Qubits(fluorescence reading) with dye stain.