CHEM 112L Experiment 27 – Paper Chromatography: Separation of Metal Cations

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Separation methods
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– crystallization, filtration, sublimation for solids, and distillation for liquids. – in addition: extraction, centrifugation – most widely method used for separation is *chromatography* – colorless solutions can be reacted to make colored solutions during separation or by other physical methods
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Types of Chromatography
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– *liquid(LC)*: includes column and high performance(HPLC) methods – *gas(GC)* – *thin layer(TLC)*: including paper chromatography – *ion-exhange* Common to all chromatography: *1) stationary phase* *2) mobile phase* – The liquid being chromatographed is separated as it is carried through the stationary phase by the flow of the mobile phase. – The components being separated must be soluble in the mobile phase and able to interact with the stationary phase – when stationary phase is in a narrow tube, it is called *column chromatography* and the mobile moves down through the column due to gravity – In *HPLC* the mobile phase is moved through the column by use of a pump exerting pressure on the system – In *TLC* the mobile phase ascends up the stationary phase due to capillary action. If paper is use it is called *paper chromatography*
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This Experiment
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– the separation of the mixture occurs because of the solubility of a given component in the mobile phase versus the interaction of that component with the paper – the *degree of partition* is the *retention factor RÆ’* – Rf = Dist. traveled by the spot / Dist. traveled by solvent front. – identity of unknown component can be established using Rf value and color – *Rf values in chromatography depend strongly upon the solvent saturation of the atmosphere above the liquid in the development chamber* – Known metal ions: *Mn2+, Co2+(purple), Cu2+(blue), Fe3+(red), and Ni2+(green)* – Mobile phase: 90/10(volume) mixture of *acetone and 6M HCL* – Reagents to treat: *ammonia and dimethylglyoxime*

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