使用氟化钡作为固定相的薄层色谱-红外光谱联用研究

原位薄层色谱-红外光谱联用在分析复杂混合物七有巨大潜力,但因固定相自身的红外吸收严重干扰样品检测,该方法进展缓慢.本文应用对中红外光透明的氟化钡微小颗粒作为固定相制备薄层层析板,并对该板的层析效果及原位显微反射红外光谱检测的可行性进行了初步的探讨.通过优化反应条件,制备出粒径为500nm左右的氟化钡颗粒;发展出一种制备薄层层析板的新技术——沉降-挥发法;通过实验证明,新型薄层板具备分离混合物的能力;原位红外光谱检测结果表明氟化钡作为固定相不干扰样品的检测.应用氟化钡作为新型薄层板固定相,为从技术上实现原位薄层色谱-红外光谱联用打开了大门.

Using barium fluoride fine particles as stationary phase for TLC/FTIR analysis

In situ TLC/FTIR technique has tremendous potential in the analysis of complex mixtures. However, the progress in this technique was quite slow. The reason is that conventional stationary phase such as silica gel etc. has strong absorption in FTIR spectrum and thus brings about severe interference in the detection of samples. To solve the problem, the authors propose to use barium fluoride fine particles as stationary phase of TLC plate. The reasons are as follows: Barium fluoride wafer has been extensively used as infrared window in FTIR experiments and it has no absorbance in an IR region between 4 000 and 800 cm'. As a matter of fact, the atomic mass of barium and fluoride is quite large, thus the normal vibration of BaF2 lattice is limited in far-IR region and low frequency part of mid-IR region. Therefore, the interference caused by IR absorption of stationary phase can be resolved if BaF2 is used as stationary phase of TLC plate. Moreover, BaF2 is quite stable and insolvable in water and most organic solvents and it will not be dissolved by mobile phase or react with samples in TLC separation. Additionally, decreasing the particle size of BaF2 is very important in TLC/FTIR analysis technique. The reason is two-fold: First, decreasing the particle size of stationary phase is helpful to improving the efficiency of separation by TLC plate; second, decreasing the size of BaFz particle can improve the quality of FTIR spectra by alleviating the problem of light scattering. By optimizing the synthetic conditions, fine particles of barium fluoride were obtained. SEM results indicate that the size of the BaF2 particles is around 500 nm. FTIR spectrum of the BaF2 particles shows that no absorption of impurity was observed. Moreover, the elevation of baseline caused by light scattering is insignificant. The authors have developed a new technique named "settlement volatilization method" to prepare TLC plate without polymeric adhesive that may bring about significant interference in FTIR analysis. Preliminary TLC experiments proved that the TLC plate using BaF2 fine particles as stationary phase can separate rhodamine B from methylene blue successfully. Applications of barium fluoride fine particles as stationary phase have bright perspective in the development of new in-situ TLC/FTIR analysis techniques.