Using Barium Fluoride Fine Particles as Stationary Phase for TLC/FTIR Analysis
LIU Xi1，2，PAN Qing-hua2，DING Jie2，3，ZHU Qing1,2, HE An-qi2，YUE Shi-juan2,4, LI Xiao-pei2，4，HU Li-ping1*， XIA Jin-ming5, LIU Cui-ge4，WEI Yong-ju4，YU Jiang3，YANG Zhan-lan2*，ZHU Xi6，XU Yi-zhuang2*，WU Jin-guang2
1. College of Pharmacy, Liaoning University Traditional Chinese Medicine, Shenyang 110032, China 2. The State Key Laboratory of Rare Earth Materials Chemistry and Application, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China 3. College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029，China 4. College of Chemistry and Material Science, Hebei Normal University, Shijiazhuang 050016, China 5. Shenyang Dootel Biopharmaceutical Research Center, Shenyang 110031, China 6. Intensive Care Unit, Peking University Third Hospital, Beijing 110083, China
Abstract：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-1. 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 BaF2 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.
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