An unusual convex-upward van Deemter curve was observed for the more retained enantiomer of a chiral sulfoxide (2-(benzylsulfinyl)benzamide) on a cellulose tris(4-chloro-3-methylphenylcarbamate)-based chiral stationary phase (CSP), prepared on silica particles of 1000 Å pore size. In contrast, the firstly eluted enantiomer of the same molecule exhibited the traditional convex-downward van Deemter curve.

A detailed kinetic and thermodynamic investigation has revealed that this unusual phenomenon, which however has already been observed in chiral chromatography, originates when the adsorption of the compound is very strong and the solid-phase diffusion negligible. Experimentally, the intraparticle diffusion of the more retained enantiomer of the sulfoxide was found to be one order of magnitude smaller than that of the first eluted one. Overall, this translates into very little longitudinal diffusion (b-term of van Deemter curve) accompanied by high solid-liquid mass transfer resistance (c-term). Finally the comparison with another, differently-substituted chiral sulfoxide (whose enantiomers both exhibit traditional van Deemter curve behavior) has allowed to correlate these findings to the specific characteristics of the molecule.

在制备的纤维素三(4-氯-3-甲基苯基氨基甲酸酯)基手性固定相 (CSP) 上，观察到手性亚砜 (2-(苄基亚磺酰基)苯甲酰胺) 的更多保留对映体存在不寻常的上凸范第姆特曲线孔径为 1000 Å 的二氧化硅颗粒。相反，同一分子的首次洗脱对映体表现出传统的凸向下的范第姆特曲线。

详细的动力学和热力学研究表明，这种不寻常的现象（在手性色谱中已经观察到）是在化合物的吸附非常强且固相扩散可忽略不计时产生的。实验发现，保留较多的亚砜对映体的颗粒内扩散比第一个洗脱的对映体小一个数量级。总体而言，这意味着非常小的纵向扩散（范第姆特曲线的b项）伴随着高固液传质阻力（ c项）。最后，与另一种不同取代的手性亚砜（其对映体均表现出传统的范第姆特曲线行为）进行比较，使这些发现与分子的具体特征相关联。