Figure 2 . Elution profiles from AEX processes employing a linear gradient elution containing 20 mM BTP, 0.001% (w/v) Pluronic F-68, 25–340 mM TEA-X at pH 9 over 90 CVs, where X is the counter-anion associated with tetraethylammonium (TEA). Depicted from top to bottom, X is tetrafluoroborate (BF4), bromide (Br), and acetate (Ac). The blue and dashed green trace correspond to A280 and the solution ionic strength, respectively. The empty peak is denoted as “Empty”, while the full peak is denoted as “Full”.