The effect of buffer pH and molarity on the HPLC separation of alkylated purines

This article describes how varying buffer pH and ionic strength affects the separation of O⁶-(2-hydroxypropyl)guanine, O⁶-methylguanine, 8-methylguanine, 7-(2-hydroxypropyl)guanine, and 7-methylguanine. The authors devised a procedure to separate C-, N-, and O-alkylguanines from one sample using two buffers: 35 mM and 125 mM ammonium phosphate (both pH 3.5). They were able to minimize the cation-exchange column degradation caused by low buffer pH.