We have a number of strategies for fixing problems with peak shape for phosphorylated compounds:

   • Ensure the column is not overloaded. We recommend an injection volume of 1 µL or less with Aqueous Normal Phase ANP methods.
• Use Teflon bottles instead of borosilicate glass for your mobile phase reservoirs. Sodium from the glass can cause peak shape problems for anionic compounds.
• Use 5–10 microM EDTA or medronic acid in the mobile phase and sample diluent. This will help chelate metals that cause problems for phosphates.
   • Try adding 0.01% ammonia to the sample diluent.
   • Use Dursan coated Cogent HPLC columns

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