In paper and thin layer chromatography the mobile phase is the solvent The

In paper and thin layer chromatography the mobile

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different components of the compound stop moving and separate from the other components. In paper and thin-layer chromatography the mobile phase is the solvent. The stationary phase in paper chromatography is the strip or piece of paper that is placed in the solvent. In thin-layer chromatography the stationary phase is the thin-layer cell. Both these kinds of chromatography use capillary action to move the solvent through the stationary phase. What is the Retention Factor, Rf? The retention factor, Rf, is a quantitative indication of how far a particular compound travels in a particular solvent. The Rf value is a good indicator of whether an unknown compound and a known compound are similar, if not identical. If the Rf value for the unknown compound is close or the same as the Rf value for the known compound then the two compounds are most likely similar or identical. The retention factor, Rf, is defined as
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Rf = distance the solute (D1) moves divided by the distance traveled by the solvent front (D2) Rf = D1 / D2 where D1 = distance that color traveled, measured from center of the band of color to the point where the food color was applied D2 = total distance that solvent traveled PAPER CHROMATOGRAPHY Chromatography is a technique that is used to separate and to identify components of a mixture. This analytical technique has a wide range of applications in the real world since many substances are mixtures of chemical compounds. In this lab, you will explore two applications of chromatography - identification of an unknown ink sample and the separation of food colorings. In paper chromatography, the sample mixture is applied to a piece of filter paper, the edge of the paper is immersed in a solvent, and the solvent moves up the paper by capillary action. Components of the mixture are carried along with the solvent up the paper to varying degrees, depending on the compound's preference to be adsorbed onto the paper versus being carried along with the solvent. The paper is composed of cellulose to which polar water molecules are adsorbed, while the solvent is less polar, usually consisting of a mixture of water and an organic liquid. The paper is called the stationary phase while the solvent is referred to as the mobile phase. Performing a chromatographic experiment is basically a three-step process: 1) application of the sample, 2) "developing" the chromatogram by allowing the mobile phase to move up the paper, and 3) calculating Rf values and making conclusions. In order to obtain a measure of the extent of movement of a component in a paper chromatography experiment, we can calculate a "Rf value" for each separated component in the developed chromatogram. A Rf value is a number that is defined as: Rf = ------------------------------------------------------------------------------ distance traveled by component from application point distance traveled by solvent from application point
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The distance traveled by the spot is measured to the MIDDLE of the spot Forensic chemistry, the profession popularized by TV's "Quincy" is the application of chemical techniques to law. Many samples that are received in a crime laboratory are complex mixtures of chemical compounds and chromatography is often ideal for separating and identifying these components. One example of this is the identification
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