Column eluant conditions were: 16 mM NaOH isocratic (inject; 0.0-2.0 min), a gradient of 16-160 mM NaOH (2.0-3 5.0 min), followed by isocratic 200 mM NaOH (35.1-40.0 min), and return to 16 mM NaOH (40.0-49.0 min) to re-equilibriate the column with the initial mobile phase prior to the next sample injection.