exp1 - Anusha Vadlamudi Partner: Christen Burns TA: Lindsay...

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Anusha Vadlamudi Partner: Christen Burns TA: Lindsay Aldridge Chem 241 Lab; Section 401; Room 300 Experiment 1: The Extraction of Ethanol from Alcoholic Beverages and the Analysis of this Extract by Gas-Liquid Chromatography (5/27/08 & 5/29/08)
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Honor Code Pledge: I pledge that no unauthorized assistance has been given or received in the completion of the work presented in this report. Introduction The analytical procedures used in this two day lab are solvent-solvent extraction and gas-liquid chromatography. The solvent-solvent extraction will be used to extract ethanol from a variety of alcoholic beverages and the amount of ethanol extracted will be determined using gas-liquid chromatography. The goal of Day 1 of the experiment is to use a calibration curve method to determine the amount of ethanol extracted and to calculate the partition coefficient and the goal of Day 2 is to used standard addition method to find the amount of ethanol in the three different beer samples, Listerine, and NyQuil. The alcoholic beverages, Nyquil, and Listerine we are going to analyze in this experiment are complex mixtures of a variety of chemical compounds. Therefore, in order to measure the ethanol content, it is important to isolate the analyte (the compound of interest; ethanol in this experiment) from the sample matrix (the rest of the chemical compounds: sugars, proteins, water etc in this experiment). The solvent-solvent technique is based on the solubility differences of the analyte in different immiscible liquids. The analyte can be extracted from one solvent to a more soluble second solvent, leaving behind the remaining compounds in the first solvent. In this experiment, pentanol will be the liquid in which the analyte (ethanol) is more soluble and the beer sample is the liquid in which the analyte is much less soluble. The beer sample can be treated as an aqueous solution due to the large amount of water in it and pentanol is the organic phase. The NaCl added to the mixture creates a charged environment, causing the ethanol molecules
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to be more attracted to the organic layer, causing them to migrate there. When the two liquids are shaken together, the ethanol will equilibrate between the two layers: ol pen aqueous OH CH CH OH CH CH tan 2 3 2 3 To quantify the ratio of concentrations of solute in each layer, the partition coefficient (K): aq ol pen aq organic OH CH CH OH CH CH S S K ] [ ] [ ] [ ] [ 2 3 tan 2 3 = = One can calculate the fraction of ethanol remaining using the equation: organic aq aq n n n q + = where n = moles of the analyte Considering that n = CV and aq organic C C K = , we can get the expression: organic aq aq KV V V q + = Since most substances will be soluble in both aqueous and organic phases, it is necessary to perform multiple extractions to isolate most of the ethanol into pentanol. The formula for the fraction of ethanol left behind after “n” extractions is: n organic aq aq KV V V q + = From this equation, it can be seen that the more extractions performed, the less ethanol
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exp1 - Anusha Vadlamudi Partner: Christen Burns TA: Lindsay...

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