The Cogent TYPE-C™ HPLC columns are very stable and can be washed between runs with 50% isopropanol or 50% methanol with 50% DI Water. Also, you can use 50% isopropanol / 50% acetonitrile or 50% methanol for very hydrophobic samples. A precaution I would give you is the stay between pH 2 and pH 7.5 when using acids and bases.
In addition the Cogent Diamond Hydride™ column should be conditioned as follows; flush the new column overnight at a low flow rate (0.1 mL/min) with 50:50 MeOH / DI water. Then in the morning, switch to whatever mobile phase you want to use and let the system equilibrate for 30 min before starting your runs. This should bring the column to a state where it will run for many injections very reproducibly. The only exception to this is where acid and ammonium additives were used on the same column. We recommend that if you want to use both types of buffers, you should have two columns.