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Team:UNIPV-Pavia/Methods Materials/Sensing ethanol concentration: our do-it-yourself kit
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We discovered that there are two different ethanol sensitive devices: the first type is based on measuring the variation of potential on a charged semiconductor, but we immediately discarded this as it was not possible for us to reproduce a similar device in the short term. | We discovered that there are two different ethanol sensitive devices: the first type is based on measuring the variation of potential on a charged semiconductor, but we immediately discarded this as it was not possible for us to reproduce a similar device in the short term. | ||
The second system looked much more achievable. Actually, it is nothing more than a colorimetric assay, where a redox reaction between a dichromate ion ("http://it.wikipedia.org/wiki/Cromo" \o "Cromo" Cr2 "http://it.wikipedia.org/wiki/Ossigeno" \o "Ossigeno" O72-) and ethanol reduces the chrome’s charge from +6 to +3 and turns the solution from orange to blue in a linear relationship with the amount of ethanol dissolved into the medium. | The second system looked much more achievable. Actually, it is nothing more than a colorimetric assay, where a redox reaction between a dichromate ion ("http://it.wikipedia.org/wiki/Cromo" \o "Cromo" Cr2 "http://it.wikipedia.org/wiki/Ossigeno" \o "Ossigeno" O72-) and ethanol reduces the chrome’s charge from +6 to +3 and turns the solution from orange to blue in a linear relationship with the amount of ethanol dissolved into the medium. | ||
| - | The components for this reaction are: | + | <!--The components for this reaction are: |
- Potassium dichromate ("http://it.wikipedia.org/wiki/Potassio" \o "Potassio" K2Cr2O7) in variable concentrations, as explained later. | - Potassium dichromate ("http://it.wikipedia.org/wiki/Potassio" \o "Potassio" K2Cr2O7) in variable concentrations, as explained later. | ||
- H2SO4 5M as solvent | - H2SO4 5M as solvent | ||
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CH3CH2OH + "http://it.wikipedia.org/wiki/Potassio" \o "Potassio" K2Cr2O7 + H2SO4 → CH3COOH + Cr2(SO4)3 + K2SO4 + 11 H2O | CH3CH2OH + "http://it.wikipedia.org/wiki/Potassio" \o "Potassio" K2Cr2O7 + H2SO4 → CH3COOH + Cr2(SO4)3 + K2SO4 + 11 H2O | ||
| + | --!> | ||
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| + | <img width="100%" height="180px" src="https://static.igem.org/mediawiki/2009/d/df/Protocol1.png" ></img> | ||
The dichromate concentration limits the range of confidence in measurement: the more dichromate ions are present, the more the system will sense higher ethanol concentrations. | The dichromate concentration limits the range of confidence in measurement: the more dichromate ions are present, the more the system will sense higher ethanol concentrations. | ||
Revision as of 15:39, 18 October 2009
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Sensing ethanol concentration: our do-it-yourself kit
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In order to sense the presence of ethanol in the culture broth, we initially used a commercial kit, which gave us disappointing results, as not even the calibration resulted linear. Then, inspired by the threat of being caught drunk by the police at the wheel, we looked into whether it was possible to set up a similar testing system to the one used by police officers for breath tests. We discovered that there are two different ethanol sensitive devices: the first type is based on measuring the variation of potential on a charged semiconductor, but we immediately discarded this as it was not possible for us to reproduce a similar device in the short term. The second system looked much more achievable. Actually, it is nothing more than a colorimetric assay, where a redox reaction between a dichromate ion ("http://it.wikipedia.org/wiki/Cromo" \o "Cromo" Cr2 "http://it.wikipedia.org/wiki/Ossigeno" \o "Ossigeno" O72-) and ethanol reduces the chrome’s charge from +6 to +3 and turns the solution from orange to blue in a linear relationship with the amount of ethanol dissolved into the medium. |
