Thin layering principles/conditions/operations/applications

related topicsThin Layer Analysis (TLC) Technology 1, Thin Layer
Chromatography
ConceptThe thin layer chromatography most commonly used also belongs to the liquid-solid adsorption chromatography. The difference with the column spectrum is that the adsorbent is coated on the glass plate to form a thin flat coating.
a
container with a small amount of expander after drying and drying at one end of the coating. The expander comes into contact with the adsorbent coating and moves upward with capillary action. As with the column chromatography process, the components in the mixture are separated into isolated sample points after multiple adsorption-dissolution between the adsorbent and the expander, and the separation of the mixture is achieved.the shape of the fixed phase and the direction of movement of the expander, the thin layer chromatography and column chromatography are basically the same in the separation principle. Because of the simple operation of thin-layer chromatography, the low dosage of samples and expanders, and the speed of development, it is often used to explore column chromatography separation conditions and monitor column chromatography processes.2, thin layer chromatography conditions (1) fixed phase selectioncolumn chromatography mentioned adsorbents can be used as a fixed phase of thin layer chromatography, separation performance and the use of selection of the same column chromatography principle is the same Commodity adsorbents are distinguished into chromatography levels (for column chromatography) and thin-layer chromatography (for thin-layer chromatography).(2) expander selectionthin-layer chromatography expander selection and column chromatography, mainly according to the polarity of the various parts in the sample, solvent for the sample of the solubility of the various parts and other factors to consider. The greater the polarity of the expander, the greater the exorcization force of the
compound
when selecting the expander, in addition to referring to the solvent polarity of the table list to choose, more use of the test method, testing on a thin sheet: (1) if the selected expander so that all the components in the mixture moved to the front of the solvent, the polarity of this solvent is too strong;(2) If the selected expander can hardly move the group points in the mixture and remains at the origin, the solvent is too polar.when a solvent does not expand the various parts well, it is often chosen to use a mixed solvent as an expander. The mixture is first expanded with a less polar solvent as the basis solvent, and if not well expanded, the polar solvent is mixed with the previous solvent, the polarity is adjusted and tested again until a suitable expander combination is selected. Suitable mixing agents often require careful selection multiple times to be determined.(3) relative movement value from the point sample origin to the edge of the expanded solvent, is the solvent moving distance, recorded as lo, the moving distance of the components in the mixture is recorded as l1, l2, l3....(4) colorisolated compounds, if there is color, it is easy to identify the various sample points. In most cases, however, the compound has no color, and to identify the sample point, the sample point must be colored. The common color-showing methods are iodine vapor color and ultraviolet color.(1) iodine vapor color: after the expanded thin sheet volatile dry expander, placed in a closed container containing iodine crystals, sublimation of iodine vapor energy and
organic
things
molecules
to form a colored consumables, complete color.(2) UV color: plate made of a fixed phase material (e.g. silicone F, alumina F, etc.) mixed with fluorescent agents, unfolded in a dry thin sheet with ultraviolet radiation, the organic matter on the board will absorb ultraviolet light, the corresponding color points appear on the board, can be observed.sometimes special color agents are used for special organic matter. At this time, it is commonly used to have a color-showing solution of the sprayer spray plate color. 3, thin-layer chromatography operation (1) plate (in silicone plate as an example) select the appropriate glass plate (often use
microscope
on the slide), in turn with water and ethanol washing, drying. Take the appropriate amount of silicone for thin layer chromatography and add the appropriate amount of distilled water to the paste. Stir slowly when modulation, so as not to create bubbles. Pour the paste over the glass plate, shake the spread out and let dry. Place in the
oven
before use and dry for 40-50 minutes around 105-115oC. Use after cooling. (2) dot sample dissolve the sample with a minimal amount of expander, take the sample solution with capillary tube, and dot the sample on a thin plate. Gently draw a thin line parallel to the bottom of the glass plate on the sample point. Thin-layer chromatography board load is limited, do not make too much sample. (3) blow-dry sample point and place it vertically in a caped expander bottle with expander. The expander should come into contact with the lower edge of the adsorbent, but do not touch the sample point. Cover and expand. To wait for the expander to go up to a certain height (the appropriate unfolding height is determined by the test), remove the thin sheet and draw the front line of the expander. (4) color, calculate the rf value volatile dry expander, choose the appropriate color method color. Measure the distance of the expander and the movement of the various parts, and calculate the relative movement value of each part. , thin-layer chromatography application (1) can be used to determine whether the two compounds are the same (whether there is the same moving value under the same expand conditions); (2) can be used to determine the group score contained in the mixture; (3) can be used to select a suitable expander for the column spectrum and monitor the separation status and effect of the column chromatography; (4) can be used to detect the reaction process.