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