Mobile-Phase Buffers, Part I-The Interpretation of pH in Partially Aqueous Mobile Phases

摘要

If liquid chromatography (LC) was performed exclusively in dilute aqueous solutions, analysts would need only an elementary understanding of pH to select and prepare buffers for mobile phases. The temptation is to apply these simple concepts to partially aqueous mobile phases, which leads to questions such as, "Why does the pH of the mobile phase change when I add methanol? Which pH is correct? What pH do I need to use?" The interpretation of pH in partially aqueous solutions is different and more complicated than it is in dilute aqueous solutions. To understand buffers in partially aqueous or nonaqueous mobile phases, chromatographers first must understand the meaning of pH in these solutions.