At YMC America, we receive quite a few inquiries regarding what is the best approach for developing analytical IEX methods that utilize salt gradients for charge variant analysis of mAbs. A relatively easy way to approach this is to use a quaternary pump HPLC and the dial-a-mix method. This enables the lab scientist to utilize all four mobile phase bottles/lines to very easily (and quickly) screen various pH conditions and salt gradients. Once the ideal conditions are determined, the method can be fine-tuned for optimal performance. The method can then be transferred to a binary HPLC system if desired, for simplicity and better reliability.