薄层色谱
薄层色谱（TLC）基于亲和力分离混合物中的化合物。TLC是一种广泛用于样品鉴定和定量的通用分离方法。薄层色谱几乎可用于分析任何类别的物质，包括农药、类固醇、生物碱、脂质、核苷酸、糖苷、糖类和脂肪酸。
在TLC中，固定相是惰性载板表面（通常是玻璃、塑料或铝）涂布的薄层吸附材料（通常是硅胶或氧化铝）。将样品点样到薄层板一端，并垂直插入装有有机溶剂（流动相）的密封室中。流动相通过毛细作用力在板上向上移动，样品各组分因其对固定相和流动相的亲和力差异而迁移不同的距离。当溶剂到达板顶端时，将薄层板从展开室中取出并干燥。分离组分呈现为薄层板上的斑点，以此计算各组分的比移值(Rf) 。
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相关技术文章
- In this article we present several HPTLC applications and analytical standards for ginsenosides.
- Thin layer chromatography
- HPTLC-MS was used to analyze stevioside and rebaudioside in artificial sweeteners, stevia plants, cola and isotonic drinks with a minimum of sample preparation.
- Thin layer chromatography (TLC), an analytical technique often used to separate and identify compounds present in a given mixture, can also be used to determine the purity of a particular substance within that mixture
- TLC plates, with silica gel, gypsum as binder, International Pharmacopoeia compliant, for identification of Atenolol and Chlorthalidone in tablets.
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相关实验方案
- What causes a dissolved mixture to separate when applied to a TLC plate? The thin-layer chromatography process relies on capillary forces. During development of the chromatogram, the mixture of substances is first transported by the mobile phase, then resides on the stationary phase for a while, and is carried along again.
- Powdered black pepper was chosen as example for dietary supplements, being a source for pierine. It is tested according to the current United States Pharmacopeia (USP) guidelines using HPTLC and HPLC.
- HPTLC was used to analyze caffeine in coffee. Filtration of coffee through a PTFE syringe filter was the only sample preparation. Quantitation was conducted with a TLC scanner.
- Silica gel G 254 plates are suitable for analysis of Dextromethorphan following the European pharmacopeia monograph.
- The modern thin-layer chromatography (TLC) offers advantages also in the field of cosmetics to quickly and simultaneously analyze samples with densitometric detection.
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薄层色谱流程和原理
薄层色谱遵循经典色谱原理，基于混合物各组分在固定相和液体流动相之间的亲和力差异进行分离。
薄层色谱比移值(Rf)
比移值(Rf)用于测量化合物的薄层板移动。Rf定义为单个组分移动距离除以溶剂移动总距离，始终在0和1之间。
| Rf = | 组分移动距离 |
| 溶剂移动距离 |
通常化合物与固定相吸附剂的结合越强，它在薄层板上的迁移就越慢。由于TLC吸附剂通常是极性的，因此非极性化合物在薄层板的移动一般较快，Rf值较高；极性化合物一般移动较慢，Rf值较低。
TLC应用
TLC广泛用于众多行业和研究领域，如制药、临床检验、环境毒理学、食品、水和农药分析以及化妆品。TLC典型应用包括：
- 食品和环境样品中药物残留和抗生素分析
- 食品和化妆品颜色、成分、防腐剂和甜味剂鉴定和定量
- 药物制剂的质控和纯度测定
- HPLC之前的快速高通量筛选
- 检查化学反应是否完成
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