二甲基亚砜对乙酸气相色谱保留时间的影响及其机理

Effect of Dimethyl Sulfoxide on the Retention Time of Acetic Acid in Gas Chromatography and Its Mechanism

通过气相色谱、红外光谱分析和量子化学计算,探究溶于二甲基亚砜(DMSO)中乙酸保留时间发生波动的原因。结果显示,乙酸保留时间变化与DMSO体积等量递增呈线性关系,R;=0.99301;根据红外光谱分析得出,DMSO和乙酸之间生成了氢键,以DMSO-乙酸分子的形式通过色谱柱;根据Gaussian09程序计算结果,DMSO电子密度大的部分给予电子,与乙酸之间形成了氢键,而DMSO电子密度小的部分容易获得电子与具有强偶极矩的色谱柱固定液聚乙二醇产生作用力,吸附在固定液上。因此,在上述一系列复杂的分子间作用力的共同影响下,乙酸保留时间发生了波动,且随着溶剂DMSO体积比增加,乙酸保留时间不断延长。

The mechanism for the fluctuation of the retention time of acetic acid dissolved in dimethyl sulfoxide(DMSO)was explored through gas chromatography,infrared spectroscopy,and quantum chemical calculations. Our results indicate that the change in retention time of acetic acid is linearly related to the increase of the volume of DMSO(R~2=0. 99301). Infrared spectroscopy analysis shows that a hydrogen bond is formed between DMSO and acetic acid,which passes through the column in the form of DMSO-acetic acid molecules. According to the calculation results of the Gaussian09 program,the high electron density portion of DMSO gives electrons and forms a hydrogen bond with acetic acid,while the portion with the low electron density can easily obtain electrons and form bonds with polyethylene glycol,a column stationary phase with a strong dipole moment,and then adsorb on the fixed liquid. Therefore,under the combined influence of this series of complex intermolecular forces,the retention time of acetic acid fluctuates,and the retention time of acetic acid increases together with the volume ratio of the DMSO solvent.