Experiment1

Experiment1 - CHEM 241L: Solvent-Solvent Extraction and...

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CHEM 241L: Solvent-Solvent Extraction and Gas-Liquid Chromatography 30 1 Experiment 1 The Extraction of Ethanol from Alcoholic Beverages and the Analysis of this Extract by Gas-Liquid Chromatography Read Section 4-8 (Chapter 4), Section 5-3 (Chapter 5), Chapter 23, and Sections 24-1 and 24-3 (Chapter 24) in Harris (7 th ed.). Note: You need to bring your laptop to lab for both days of this experiment BACKGROUND & THEORY In this experiment students will be introduced to the use of solvent-solvent extraction and gas-liquid chromatography for the separation and analysis of complex mixtures. Specifically, students will extract the ethanol (CH 3 CH 2 OH) from a variety of alcoholic beverages and then use gas-liquid chromatography to qualitatively analyze the extract and quantitatively determine the amount of ethanol that was extracted from the beverage samples. By the end of this lab students will have learned how to perform a solvent-solvent extraction in order to remove a chemical compound from a complex mixture, will have gained hands on experience with the use of a gas chromatograph for chemical analysis, will have learned how to construct and use both standard calibration and standard addition plots, will have learned how to experimentally determine the partition coefficient of a solute molecule, and will have learned how to evaluate chromatographic peaks using integration methods. Reading Assignment
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CHEM 241L: Solvent-Solvent Extraction and Gas-Liquid Chromatography 31 Solvent-Solvent Extraction Many real world samples (soil, milk, beer, soda, drugs etc…) are complex mixtures containing a wide variety of chemical compounds. For instance, the alcoholic beverages you will be analyzing in this experiment contain alcohol, carbohydrates (sugars), proteins, and water. Because of the complex nature of most real world samples a direct analysis using one method is typically not feasible, due to the fact that some of the chemical compounds can interfere with the analysis. To avoid this problem it is often necessary to remove or isolate the compound of interest (the analyte ) from the rest of the chemical compounds in the sample (the sample matrix ). One way to accomplish this is to transfer the analyte from one solvent, which contains all the other compounds in the sample, to a second solvent in which only the analyte is soluble. This simple technique is called solvent-solvent extraction and it is based on differences in solubility of the analyte in different liquids. If the solvents are chosen correctly, the analyte can be extracted from one solvent to another because it is more soluble in the second solvent than the first. In addition, the remaining compounds in the sample matrix are not as soluble in the second solvent so they remain behind in the first solvent. One criteria that is necessary for solvent-solvent extraction to work is that the two solvents are not miscible (mix freely) with one another and thus form two separate and distinct layers or
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Experiment1 - CHEM 241L: Solvent-Solvent Extraction and...

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