PP-ODS2 column needs to be washed. If the standard protocol as outlined in the user manual doesn’t solve the problem, proceed to wash the column as follows:
1. 30 min water in the reverse direction at half the normal flow rate.
2. 1 hr with 0.1% phosphoric acid in 100% acetonitrile in the reverse direction
3. 30 min water in the normal direction
4. Run analytical mobile phase overnight to lower the BGC.
5. Re-check the separation.