Our stability study shows that unmodified oligos are stable > 6 years by storing them lyophilised at -20 °C or below:

The stability study has been performed using the analytical methods HPLC and MALDI-TOF MS as well as application based in DNA sequencing.

Once you have dissolved your oligonucleotides in sterile water or buffered solutions (or you have already received your oligonucleotide in the requested solution), the best way to store them is to prepare aliquots of several tubes, to lyophilise the aliquots, and to store them at -20 °C.

The sample which is currently in use can be kept in a refrigerator at +4° C for a short time to avoid continuous freezing and thawing of the solution.