…but there is some evidence that the use of phosphoric acid may semi-permanently change the surface chemistry, and therefore the chromatography of the column.
For example, if you get a certain separation using formic acid and then introduce phosphoric acid to the column, you may not get the same separation when you try the formic acid method again. For this reason, you should keep the column dedicated to phosphoric acid use only.
Also the column should never be used with LCMS because of the incompatibility with phosphates.
*Yes, phosphoric acid or sodium phosphate can be used with the Cogent Diamond Hydride HPLC column, but keep in mind the recommended pH range of 2.5 to 7. It would be suggested to use low amounts of these additives at first, (i.e. beginning with 0.01%) but ideally 0.1% formic acid works very well and is easily translated to LCMS.