Why are my oligos a yellow/brown color?
Customers who are new to working with large amounts of material are sometimes surprised when they see a yellow or brown discoloration to their oligos. If you have experienced this, do not worry. Color variation is normal in custom synthesis, especially as concentration increases. Importantly, IDT does not expect this to affect oligo function in our customers' experimental applications.
The image above depicts normal color variation as seen in oligo pools which are formulated to the same concentration (200 nmol oligos in 15 mL solution). In general, modified oligos at larger scales are more likely to display the variation seen above, while small-scale unmodified oligos (e.g., 25 nmol) tend to remain colorless in solution.