Studies Of In Situ Thin-layer Chromatography Coupled With Fouirer Transform Infrared Spectroscopy Technique

TLC-FTIR technique has huge advantages in separating and identifying of complexmixtures. However, conventional TLC stationary phase, such as silica gel, has a strongabsorption in mid-IR region and brings about severe interference in the detection of samples.To solve the problem, we proposed to use Al₂O₃as stationary phase of TLC plate. Weprepared Al₂O₃powers at1200℃with AlCl₃.6H₂O and CO（NH₂）₂as raw materials. Thepowers were analyzed by IR spectrum, Nano particle size test, scanning electron microscopyanalysis. The experimental results showed that Al₂O₃was pure, and it had no absorption in theIR region. The particle size was about200nm-300nm. We prepared TLC plate of Al₂O₃by"settlement volatile method" and made some separation experiments. Results showed that theTLC plate had a perfect separation ability. IR spectra demonstrated that the TLC plate ofAl₂O₃absorbed considerable amount of water. The absorbed water cannot be removed andcaused adverse influence to sample identification. To solve the problem, we proposed toprepare TLC plate with dry powders. However, the sample had a quite slow migration speedand there was a serious trailing effect. To find out the reason, we prepared narrow-band TLCplate with high concentration of suspension liquids. The separation effect was greatlyimproved, but FTIR spectra of components after development showed obvious differencefrom its standard spectrum. Thus, Al₂O₃cannot yet be applied as TLC stationary phase for insitu TLC-FTIR analysis.The third and fourth chapters focus on further development of silver iodide as stationaryphase for TLC/FTIR analysis. In previous work, we found that the sensitivity of TLC-FTIRanalysis is quite low, only when the concentration of the sample is higher than0.5%, thespectra of components can be observed. To solve the problem, we proposed to usenarrow-band TLC plate instead of common TLC plate. Experimental results showed thedetect limit of TLC-FTIR analysis can be improved significantly. Besides, the preparation ofnarrow-band TLC plate reduced the usage of stationary phase and saved experiment cost.Preparation efficiency was improved obviously. The preparation time of TLC plate wasshortened to within0.5h from3-7days. In addition, we also performed narrow-band TLCplate to analyze colorless sample. With the help of Matlab software, IR spectra of thecomponents after separation on TLC plate was analyzed by IR-mapping.