Analytical procedures: extractions, separations, purifications, etc.
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| Experiment 1 | The Extraction of Ethanol from Alcoholic Beverages and the Analysis of this extract by gas-liquid chromatography.
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| What two procedures will be used? | solvent to solvent extraction and gas-liquid chromatography.
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| solvent-solvent extraction | extract ethanol from a variety of alcoholic beverages (complex mixtures: beer samples in this case).
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| gas-liquid chromatography | quantitatively analyze the extract and quantitatively determine the amount of ethanol that was extracted.
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| what 5 things will be learned after the experiment? | 1. Solvent-to-solvent extraction
2.Gas-liquid chromatography
3. Standard calibration/standard addition plots
4. Experimental partition coefficient of solute
5. Evaluate chromatography peaks using integration methods.
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| alcoholic beverages contain: | alcohol, carbohydrates (sugars), proteins, and water.
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| analyte | compound of interest
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| sample matrix | rest of the chemical compounds in the sample besides the analyte.
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| solvent-to-solvent extraction | to transfer the analyte from one solvent, which contains all other compounds in the sample, to a second solvent in which only the analyte is soluble. It is based on differences in solubility of analyte in different liquids.
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| why is the analyte extracted from one solvent to the other? | because it is more soluble in the second solvent than the first and the remaining compounds in the sample matrix are not as soluble so the remain behind.
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| criteria for solvent to solvent extraction to work : | the two solvents are not miscible (mix freely) with one another and thus form two separate and distinct layers/phases. The aqueous and the organic phases.
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| how will you remove the ethanol from the beer samples? | by adding some pentanol, an organic solvent, to the beer sample (has water: aqueous) and mixing the two.
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| what happens essentially when mixing the two solvents? | the solute redistributes itself between the two liquid phases and it forms an equilibrium.
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| partition coefficient (K) | the ratio of the concentrations of solute in each layer.
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| partition coefficient equation: | word
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| fraction in moles of ethanol remaining in the aqueous layer (q) by using volumes of solvents. | word
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| The fraction of solute left behind after n extractions is: | word
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| what is q and what is q-1? | q: fraction of solute left behind
q-1: fraction of solute extracted
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| gas chromatography | for separation and analysis of volatile organic compounds that are not thermally labile. commonly used to determine purity of substances, separate components of mixtures, quantitate relative amounts of components, and qualitatively identify compounds.
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| gas chromatography is based on: | the differential migration of chemical species through some medium.
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