“My results deteriorated after two days of using the Diamond Hydride column for AMP, ADP, ATP, UDP and GPT in biological extracts”.
Phosphate containing metabolites that you are using are very sensitive to the presence of sodium in your LC-MS system.
After few days there is enough sodium in your system (leaching from the borosilicate glass bottles) that it is sufficient to affect peak shape of this class of metabolites. There are two solutions to this problem. You can:
A: Prepare fresh mobile phase daily or
B: Switch to Teflon moble phase reservoir bottles.
We recommend point B above for a long term solution. If you happen to have J.T. Baker Nitric Acid – ULTREX made in Canada, it comes in perfect Teflon bottles. To prepare these bottles for use with LC-MS, rinse them with DI water (3 times), fill with methanol/DI water 1:1 and keep this solution overnight in the bottle. After this the bottles are ready for LC-MS
You can also try adjusting the aqueous ammonium acetate or formate mobile phase to pH 7.0 using ammonia. Also you can try adding 0.1% ammonia to the sample diluent and see if this remedies the peak shape issue. The sample may not be able to be stored as long with the ammonia however. Also be sure to dedicate one column to ammonium acetate/formate and anothe to acids such as formic acid.