The presence of anionic free silanols in the silica-based stationary phases gives rise to broad and asymmetrical peaks when cationic basic compounds are chromatographed using hydro-organic mobile phases. The addition to the mobile phase of a reagent with ionic character prevents the access of analytes to the free silanols, improving the peak shape. The silanol activity can be affected by the buffer concentration and mobile phase pH, factors that are not always considered sufficiently in the literature. In this work, the chromatographic behaviour of three basic β‐adrenoceptor antagonists (acebutolol, nadolol and timolol), using mobile phases containing acetonitrile, was examined at different phosphate buffer concentrations (5–50 mM) and mobile phase pH (2–8), in the absence and presence of three imidazolium-based ionic liquids (1‐ethyl-, 1‐butyl- and 1-hexyl-3-methylimidazolium chloride). All factors were evaluated through both the retention and peak shape. The imidazolium cations can block the access of cationic analytes through electrostatic interaction with the anionic silanols, or association with the alkyl chains bound to the stationary phase. In previous reports, the protection mechanism was demonstrated to be directly related to the cation size. The studies in this work reveal that the effectiveness of the mobile phase additive as silanol blocker also depends on the concentration of the buffer anion and the protonation degree of the silanols on the stationary phase. Increasing amounts of phosphate at low pH give rise to increasing retention times. Also, the peak shape is improved, which indicates the influence of phosphate on blocking the activity of free silanols. However, the benefits obtained by the combined effect of buffering the mobile phase at low pH and the use of a bulky additive are lost at pH > 6.

当使用氢有机流动相色谱分离阳离子碱性化合物时，二氧化硅基固定相中阴离子游离硅烷醇的存在会产生宽峰和不对称峰。具有离子特性的试剂在流动相中的加入会阻止分析物进入游离的硅烷醇，从而改善了峰形。硅烷醇活性可能受缓冲液浓度和流动相pH的影响，这些因素在文献中并不总是被充分考虑。在这项工作中，使用了含乙腈的流动相，在不同的磷酸盐缓冲液浓度（5-50 mM）和流动相pH（2-8）下，对三种基本的β-肾上腺素受体拮抗剂（醋丁洛尔，纳多洛尔和噻吗洛尔）的色谱行为进行了研究。 ，在不存在三种咪唑基离子液体（1-乙基-，1-丁基和1-己基-3-甲基咪唑氯化物）。通过保留率和峰形对所有因素进行了评估。咪唑阳离子可以通过与阴离子硅烷醇的静电相互作用或与固定相结合的烷基链缔合，从而阻止阳离子分析物的进入。在以前的报告中，该保护机制被证明与阳离子的大小直接相关。这项工作中的研究表明，流动相添加剂作为硅烷醇阻滞剂的有效性还取决于缓冲液阴离子的浓度和固定相上硅烷醇的质子化程度。在低pH下增加磷酸盐的用量会增加保留时间。同样，峰形得到改善，这表明磷酸盐对阻断游离硅烷醇活性的影响。然而，