薄层色谱中识别和检测的特殊考虑因素

Thin Layer chromatography presents a low cost, simple and sensitive option for identification and estimation of individual components in a mixture of components. The popular choices offered arePaper chromatographyand HPTLC or High Performance Thin layer chromatography. Each of these techniques comprises essentially of a plane surface of paper or a metallic glass plate coated with an appropriate adsorbent with the help of a binder. The mobile phase drives the sample components by capillary action or gravitational force in case of suspended plates

Thin layer chromatographyhas found wide range of applications in drug development, organic chemistry research, foods, forensics, biochemical separations and research. Although the technique is simple and affords a visual display of separated spots the accuracy and precision is dependent on the technique adopted for application of sample spots, development and quantification of separated components.

延迟因子RF.

Retardation factor is an important parameter in thin layer determinations. It defines the distance travelled by the mixture component from application or starting point relative to the distance travelled by the solvent front over a given time period. Rf lies between 0 and 1.0. Ideally two spots should not overlap with each other.

RF受到纸张或溶剂混合物中的杂质，温度和显影室内蒸气的饱和度的影响。

Choice of Solvent Mixtures

Judicious choice of solvent mixtures is critical and in thin layer separations. Special attention should be placed on the following aspects:

• 选择的溶剂应该彼此完全混溶
• 溶剂应朝向样品混合物组分化学惰性
• Any of the solvent component should not be volatile to an extent that can result in changes in the composition of sample mixture over the development time
• The solvent should not result in distortion of spots through tailing

The minimum separation between two closely spaced spots should have Rf between 0.05 and 0.1

Detection of spots

在该阶段中，标记溶剂前线并干燥溶剂。常用的实践是用吹风机的天然空气干燥或干燥，以加速干燥。然而，切勿将吹风机悬挂在靠近板上，以防止局部加热。

The technique for characterization and evaluation of spots include

• Natural colour observation as in case of coloured compounds
• 用颜色产生试剂的络合反应
• Spraying for inducing fluorescence
• 放射性的测量

Iodine vapour is used for visualisation of colourless or non-fluorescent spots. Other commonly used reagents are :

Reagent	Typical compounds
茚三酮	氨基酸
2,4 - 二硝基苯肼	艾尔dehydes&Ketones
Chloroplatinic acids	艾尔kaloids
菠萝蛋白蓝色	脂质

市售板可用于吸附剂中的荧光染料。在UV观察柜中握住斑点板，斑点呈发光并变得可见，并且由于荧光性能而变得可见。

The two plates can be photographed before disposal to retain permanent record of separations as the plates have a tendency to fade with time.