Legg Michael A, Wirth Mary J
Department of Chemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, USA.
Anal Chem. 2006 Sep 15;78(18):6457-64. doi: 10.1021/ac060820f.
Atomic force microscopy was used to study surface characteristics of three chromatographic silica products: Agilent Zorbax SB300, Waters Symmetry 300, and Merck Chromolith. Each is modified with a monomeric C18 monolayer. Both topographic and adhesive force measurements were made for each product. Topographical images revealed that all three materials are as smooth as glass on the scale of 100 nm and below. Adhesive forces for all three materials were much lower and much more uniform than for chemically modified fused silica. FT-IR spectra for all three materials showed a low abundance of isolated silanols, thus explaining the low adhesion. Chromatograms of a cationic dye, 1,1'-didodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), ranging in concentration from 1 to 300 microM were obtained for each column. All three materials exhibited classic nonlinear tailing; the Zorbax exhibited fronting as well. Chromatographic simulations were performed for the Symmetry and Chromolith products to determine the number of strong adsorption sites. The AFM, FT-IR, and HPLC were all consistent in indicating that the Chromolith material had half as many strong adsorption sites as the Symmetry material. The Zorbax material exhibited a number of isolated silanols that was comparable to the other materials, yet its adhesive force suggested a less adsorptive material, and its chromatographic performance suggested a more adsorptive material. Its topography is discussed as a possible reason for its anomalous chromatographic behavior.
安捷伦Zorbax SB300、沃特世Symmetry 300和默克Chromolith。每种产品都用单体C18单分子层进行了改性。对每种产品都进行了形貌和粘附力测量。形貌图像显示，在100纳米及以下尺度上，所有三种材料都像玻璃一样光滑。与化学改性的熔融石英相比，所有三种材料的粘附力都低得多且更加均匀。所有三种材料的傅里叶变换红外光谱显示孤立硅醇的丰度较低，因此解释了低粘附性的原因。对每根色谱柱获得了浓度范围为1至300微摩尔的阳离子染料1,1'-二癸基-3,3,3',3'-四甲基吲哚羰花青高氯酸盐（DiI）的色谱图。所有三种材料都表现出典型的非线性拖尾；Zorbax还表现出前沿峰。对Symmetry和Chromolith产品进行了色谱模拟，以确定强吸附位点的数量。原子力显微镜、傅里叶变换红外光谱和高效液相色谱结果均一致表明，Chromolith材料的强吸附位点数量是Symmetry材料的一半。Zorbax材料的孤立硅醇数量与其他材料相当，但其粘附力表明它是吸附性较弱的材料，而其色谱性能表明它是吸附性较强的材料。文中讨论了其形貌可能是其异常色谱行为的原因。
