Espinosa Sonia, Bosch Elisabeth, Rosés Marti
Departament de Química Analítica, Universitat de Barcelona, Spain.
Anal Chem. 2002 Aug 1;74(15):3809-18. doi: 10.1021/ac020012y.
The addition of acetonitrile to aqueous buffers to prepare RP HPLC mobile phases changes the buffer properties (pH and buffer capacity). This variation is studied for ace tate, phosphate, phthalate, citrate, and ammonia buffers in acetonitrile-water mixtures up to 60% in acetonitrile (v/v). Equations are proposed to relate pH and buffer capacity change of these buffers to the initial aqueous pH value and to the volume fraction of acetonitrile added. It is demonstrated that the pH change of the buffer depends not only on the initial aqueous pH of the buffer and on the percentage of acetonitrile added but also on the particular buffer used. The proposed equations allow an accurate prediction of this ionization for the studied buffers. Since the retention of acid/base compounds shows a strong dependence of their degree of ionization, the equations are used to predict the change in this ionization with addition of acetonitrile when the RP HPLC mobile phase is prepared. This prediction allows estimation of the retention of an acid/base compound in a particular acetonitrile-water buffered mobile phase.
向水性缓冲液中添加乙腈以制备反相高效液相色谱（RP HPLC）流动相时，会改变缓冲液的性质（pH值和缓冲容量）。本文研究了在乙腈 - 水混合物中乙腈含量高达60%（v/v）时，乙酸盐、磷酸盐、邻苯二甲酸盐、柠檬酸盐和氨缓冲液的这种变化情况。提出了一些方程式，用于将这些缓冲液的pH值和缓冲容量变化与初始水性pH值以及添加的乙腈体积分数相关联。结果表明，缓冲液的pH值变化不仅取决于缓冲液的初始水性pH值和添加的乙腈百分比，还取决于所使用的特定缓冲液。所提出的方程式能够准确预测所研究缓冲液的这种电离情况。由于酸碱化合物的保留情况与其电离程度密切相关，因此这些方程式可用于预测制备RP HPLC流动相时添加乙腈后电离情况的变化。这种预测有助于估算酸碱化合物在特定乙腈 - 水缓冲流动相中的保留情况。
