Mouthwash Gas Chromatography
ANALYSIS OF MOUTHWASH
Background Information:
Commercial mouthwashes are mixtures of water, alcohol, dyes, flavorings, and other compounds. In this experiment, you will use gas chromatography to determine the alcohol content of the mouthwash. Since the volumes of alcohol and water are not additive when mixed, a calibration curve must be used. It will provide the correction factor needed for alcohol-water mixtures. The calibration curve will be prepared by placing a known amount of alcohol in an alcohol-water mixture. The observed percentage of alcohol will be plotted against the true percentage of alcohol.
Equipment/Materials:
95% ethanol distilled water gas chromatograph (w/10 μL syringe) mouthwash samples
Procedure: …show more content…
Prepare standard solutions of ethanol according to the following amounts.
|% volume alcohol |95% alcohol (mL/100 mL) |
|5% |5.26 |
|10% |10.53 |
|20% |21.05 |
|30% |31.58 …show more content…
Obtain 1.0 μL of a mouthwash sample and about 5 μL of air. Label the mouthwash injected and attenuation. Follow the same procedure for each mouthwash sample. Rinse the syringe with toluene between injections.
Data Analysis: 1. Determine the retention time of the 95% alcohol. 2. Use the retention time to identify the alcohol peaks of the standard solutions and mouthwash samples. 3. Determine the area under each alcohol peak by measuring the height of the peak and the width at ½ the height. Use the following equation to calculate the area. Area = ½ (width)(height)(attenuation) 4. Prepare a calibration curve of the standard solutions: % area alcohol (y-axis) vs. % alcohol (x-axis). Draw a best-fit line. 5. Use the calibration curve to determine the % alcohol in the mouthwash samples. 6. For the accepted value of % alcohol, record the % alcohol from the inactive ingredient list on the mouthwash. 7. Calculate your % error.
Data Table:
|% volume alcohol |Height (cm) |Width (cm) |Alcohol Area (cm2) |
|5% | | | |
|10% | | |
Background Information:
Commercial mouthwashes are mixtures of water, alcohol, dyes, flavorings, and other compounds. In this experiment, you will use gas chromatography to determine the alcohol content of the mouthwash. Since the volumes of alcohol and water are not additive when mixed, a calibration curve must be used. It will provide the correction factor needed for alcohol-water mixtures. The calibration curve will be prepared by placing a known amount of alcohol in an alcohol-water mixture. The observed percentage of alcohol will be plotted against the true percentage of alcohol.
Equipment/Materials:
95% ethanol distilled water gas chromatograph (w/10 μL syringe) mouthwash samples
Procedure: …show more content…
Prepare standard solutions of ethanol according to the following amounts.
|% volume alcohol |95% alcohol (mL/100 mL) |
|5% |5.26 |
|10% |10.53 |
|20% |21.05 |
|30% |31.58 …show more content…
Obtain 1.0 μL of a mouthwash sample and about 5 μL of air. Label the mouthwash injected and attenuation. Follow the same procedure for each mouthwash sample. Rinse the syringe with toluene between injections.
Data Analysis: 1. Determine the retention time of the 95% alcohol. 2. Use the retention time to identify the alcohol peaks of the standard solutions and mouthwash samples. 3. Determine the area under each alcohol peak by measuring the height of the peak and the width at ½ the height. Use the following equation to calculate the area. Area = ½ (width)(height)(attenuation) 4. Prepare a calibration curve of the standard solutions: % area alcohol (y-axis) vs. % alcohol (x-axis). Draw a best-fit line. 5. Use the calibration curve to determine the % alcohol in the mouthwash samples. 6. For the accepted value of % alcohol, record the % alcohol from the inactive ingredient list on the mouthwash. 7. Calculate your % error.
Data Table:
|% volume alcohol |Height (cm) |Width (cm) |Alcohol Area (cm2) |
|5% | | | |
|10% | | |