일반화학실험 A+레포트/탄수화물 정성실험 Thin layer chromatography(TLC)

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• 1. Thin layer chromatography(TLC)

  TLC는 크로마토그래피 중 하나이다. 크로마토그래피는 다성분 혼합물을 두 상(phases) 즉, 고정상(stationary)과 이동상(mobile phase)에 분배시켜, 각 성분들이 두 상에 분배되는 정도, 즉 각 상에 대한 용해도나 흡착도가 달라 다른 분배 평행계수를 보이기 때문에 분배가 가능하다. 일종의 연속적인 추출과정으로, 고정상에 대해 연속상으로 이동상을 접촉시키면서 이동시키면 이동되면서 각 상에 있던 물질들은 새로운 고정상을 접할 때마다 재분배되고, 고정상에 많이 분배되는 성분들의 이동속도는 늦어지고 이동상에 분배가 많이 되는 성분의 이동속도는 빨라지게 되어 분리된다.

• 2. 이동상

  이동상은 시료와 함께 이동하는 상에 비해 시료와 함께 이동하지 않는 상이다. 순수한 실리카 및 알루미나 정지상을 사용하는 크로마토그래피에서 용매의 용리력은 그 극성에 따라 증가한다(예: 핵세인-아세톤-알코올-물). 혼합 용매는 얇은 층을 따라 올라가면서 크로마토그래피에 의해 분리되어 판 위에서의 거리에 따라 용매 조성이 연속적으로 변하게 되므로 가능하면 단일 용매 또는 많아야 2~3가지 용매만을 사용해야 한다.

• 3. 고정상

  TLC의 약 80%는 비변형된 60ANGSTROM 기공 크기의 실리카 정지상을 사용하고 있다. 극성이 높은 silica gel, alumina 등이 정지상으로 사용된다. 가장 많이 사용되는 지지체는 고순도, 구형의 미공성 입자(microporous particle) 실리카로서, 용매에 대한 투과성이 있으며, 실리카 1g당 표면적이 수백 m^{2}이다. 실리카 표면은 1m^{2}당 최대 8mu mol의 실란올(Si-OH)기를 포함한다.

• 4. Rf 값

  R_{f} (Rate of Flow, 이동률)결과를 정량화하기 위해 출발점으로부터 성분 반점들까지의 거리를 용매가 이동한 용매선까지의 거리로 나누어준 R_{f}을 사용한다. 이는 화합물과 사용하는 전개제의 종류에 따라 독특한 값을 나타내기 때문에 물질의 확인에 매우 유용하다. Rf값이 높다면 전개용매가 극성일수록 compound의 인력은 증가한다. 비극성 화합물일수록 silicagel과의 인력은 감소한다. 반면 Rf값이 낮다면 극성화합물일수록 silicagel과의 인력이 증가하는 것이다.

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• 1. Thin layer chromatography(TLC)

  Thin layer chromatography (TLC) is a widely used analytical technique in various fields, including chemistry, biochemistry, and pharmaceutical sciences. TLC is a simple, rapid, and cost-effective method for separating and identifying components in a mixture. The technique involves the use of a thin layer of adsorbent material, typically silica gel or alumina, coated on a solid support, such as a glass or plastic plate. The sample is applied to the bottom of the plate, and a solvent or a mixture of solvents (the mobile phase) is allowed to move up the plate by capillary action. As the mobile phase travels up the plate, the components in the sample separate based on their relative affinities for the stationary phase and the mobile phase. The separated components can then be visualized using various detection methods, such as UV light or chemical reagents. TLC is a versatile technique that can be used for a wide range of applications, including qualitative and quantitative analysis, identification of compounds, and monitoring the progress of chemical reactions. Its simplicity, speed, and flexibility make it an essential tool in many analytical laboratories.

• 2. 이동상

  The mobile phase, also known as the eluent, is a crucial component in thin layer chromatography (TLC). The mobile phase is the solvent or mixture of solvents that travels up the TLC plate, carrying the sample components with it. The choice of the mobile phase is crucial in determining the separation and resolution of the components in the sample. The mobile phase should be selected based on the polarity and solubility characteristics of the sample components, as well as the nature of the stationary phase. Generally, a more polar mobile phase is used for more polar sample components, while a less polar mobile phase is used for less polar components. The composition of the mobile phase can also be adjusted to optimize the separation, such as by varying the ratio of different solvents or adding modifiers like acids or bases. The flow rate of the mobile phase is also an important factor, as it can affect the separation and resolution of the components. Overall, the careful selection and optimization of the mobile phase is essential for achieving effective separation and identification of the components in a TLC analysis.

• 3. 고정상

  The stationary phase in thin layer chromatography (TLC) is the adsorbent material coated on the solid support, such as a glass or plastic plate. The choice of the stationary phase is crucial in determining the separation and resolution of the sample components. The most common stationary phases used in TLC are silica gel and alumina, which are polar adsorbents. These materials have a high surface area and can interact with the sample components through various mechanisms, such as adsorption, ion exchange, and hydrogen bonding. The polarity of the stationary phase can be modified by the addition of functional groups, such as amino or cyano groups, to create different types of stationary phases for specific applications. The particle size and pore size of the stationary phase can also affect the separation efficiency, with smaller particle sizes and larger pore sizes generally providing better separation. The choice of the stationary phase should be based on the nature of the sample components, the desired separation, and the specific application. Proper selection and optimization of the stationary phase are crucial for achieving effective separation and identification of the components in a TLC analysis.

• 4. Rf 값

  The Rf (Retention factor) value is a crucial parameter in thin layer chromatography (TLC) that provides information about the separation and identification of the components in a sample. The Rf value is defined as the ratio of the distance traveled by a component on the TLC plate to the distance traveled by the mobile phase. The Rf value ranges from 0 to 1, with 0 indicating that the component is completely retained on the stationary phase and 1 indicating that the component is completely eluted with the mobile phase. The Rf value of a component depends on various factors, including the polarity of the component, the polarity of the stationary phase, the composition of the mobile phase, and the experimental conditions, such as temperature and humidity. By comparing the Rf values of the sample components with those of known standards, it is possible to identify the components in the sample. The Rf value is also useful for monitoring the progress of a chemical reaction or for quantitative analysis, as the Rf value can be correlated with the concentration of the component. Accurate determination and interpretation of Rf values are essential for effective separation and identification of components in TLC analysis.