Hi!
I wanted to do a continuation of my science project from last year, which dealt with water quality. This year, I am looking into water contamination from plastics. So far, my research has shown that the most common chemicals are plasticizers (mostly phthalates) and Bisphenol-A (BPA).
It seems that testing for phthalates involves advanced equipment of spectrometers that can only be found in private labs. Is there a method to test in a high school lab?
In addition, I learned that BPA can be tested for using Iron (III) chloride as an indicator for color change. What would be the most effective method? Could I also use a visible light spectrometer to quantitatively measure for the color change by comparing the sample to a standard? I also am still debating about what to specifically test with plastic chemicals and water.
Any insight would truly be appreciated! Thank you in advance!
Water Contamination
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norman40
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Re: Water Contamination
Hi Sophia2101,
Unfortunately the available test methods for phthalates use separation and spectrometric techniques. Specialized equipment is needed for both. So I think you'd need access to a well-equipped lab to test for phthalates.
An iron chloride solution can be used as an indicator for phenolic compounds like BPA as described here:
https://en.wikipedia.org/wiki/Ferric_chloride_test
As you've pointed out, the iron chloride test only indicates presence. It might be possible to develop a quantitative version of the iron chloride test using a visible light spectrometer as you suggest. This kind of test technique is described in the following Science Buddies project:
https://www.sciencebuddies.org/science- ... rts-drinks
To follow this test technique you'd need to prepare a calibration curve with different concentrations of iron chloride/BPA. If you can observe a good relationship between concentration and light absorbance you might be able to work out a quantitative test.
I hope this helps. Please post again if you have more questions.
A. Norman
Unfortunately the available test methods for phthalates use separation and spectrometric techniques. Specialized equipment is needed for both. So I think you'd need access to a well-equipped lab to test for phthalates.
An iron chloride solution can be used as an indicator for phenolic compounds like BPA as described here:
https://en.wikipedia.org/wiki/Ferric_chloride_test
As you've pointed out, the iron chloride test only indicates presence. It might be possible to develop a quantitative version of the iron chloride test using a visible light spectrometer as you suggest. This kind of test technique is described in the following Science Buddies project:
https://www.sciencebuddies.org/science- ... rts-drinks
To follow this test technique you'd need to prepare a calibration curve with different concentrations of iron chloride/BPA. If you can observe a good relationship between concentration and light absorbance you might be able to work out a quantitative test.
I hope this helps. Please post again if you have more questions.
A. Norman
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sophia2101
- Posts: 5
- Joined: Tue Dec 29, 2015 3:36 pm
- Occupation: Student
Re: Water Contamination
Thank you so much for your response!
I have decided to continue with BPA detection in plastics. So far, I have used the ferric chloride test, in which I received positive results most prominently in thermal paper (store receipts), although not much else.
However, I can have my samples measured in a UV-vis spectrophotometer.
My (condensed) procedure is as follows:
1. Melt the plastic sample in boiling water with methanol (to act as a solvent) for ten minutes.
2. Place the liquid sample into a cuvette. Also have a blank sample of just distilled water.
3. Place the sample cuvette and blank cuvette into the UV-vis spectrophotometer. Use the wavelength range of 200nm-300nm (? - this was what I found as the range BPA absorbs).
4. Using the readings (maximum absorption wavelength and absorbance) and the Beer Lambert Law, calculate concentration.
Would this be a valid procedure and provide plausible results?
In addition, as a result of this experiment, would people be more interested in discovering the BPA concentration in various household items (as this shocked me in my research), or discovering the relationship between temperature and BPA concentration?
Any insight is greatly appreciated! Thank you!
I have decided to continue with BPA detection in plastics. So far, I have used the ferric chloride test, in which I received positive results most prominently in thermal paper (store receipts), although not much else.
However, I can have my samples measured in a UV-vis spectrophotometer.
My (condensed) procedure is as follows:
1. Melt the plastic sample in boiling water with methanol (to act as a solvent) for ten minutes.
2. Place the liquid sample into a cuvette. Also have a blank sample of just distilled water.
3. Place the sample cuvette and blank cuvette into the UV-vis spectrophotometer. Use the wavelength range of 200nm-300nm (? - this was what I found as the range BPA absorbs).
4. Using the readings (maximum absorption wavelength and absorbance) and the Beer Lambert Law, calculate concentration.
Would this be a valid procedure and provide plausible results?
In addition, as a result of this experiment, would people be more interested in discovering the BPA concentration in various household items (as this shocked me in my research), or discovering the relationship between temperature and BPA concentration?
Any insight is greatly appreciated! Thank you!
-
norman40
- Former Expert
- Posts: 1022
- Joined: Mon Jul 14, 2014 1:49 pm
- Occupation: retired chemist
- Project Question: Volunteer
- Project Due Date: n/a
- Project Status: Not applicable
Re: Water Contamination
Hi Sophia2101,
The procedure you've outlined includes the many of the steps needed for finding the BPA concentration from UV absorption data. But there are some additions and modifications needed.
Usually the wavelength that gives maximum absorption is used for all testing. The maximum can be found by measuring the UV absorbance at several wavelengths between 200nm and 300nm. Set the spectrophotometer to the wavelength that gave the highest absorbance and leave it there for your tests.
To find the BPA concentration from UV absorbance data, you'll need to make a calibration curve. Make a stock solution of BPA in water and use it to prepare several diluted solutions of different concentrations. Measure the UV absorbance for each of the diluted solutions. Make a graph with the solution concentrations on the x-axis and absorbance on the y-axis. You can use this calibration curve to find the concentration on an unknown sample given its UV absorbance.
The following links have more details on finding the maximum wavelength and making a calibration curve:
http://www.umich.edu/~chem125/softchalk ... print.html
http://chemistry.bd.psu.edu/jircitano/beerslaw07.pdf
I'm not sure of the need for methanol in your extraction step. You might want to try placing the plastic sample in boiling (or hot) water to see if you extract any BPA. Or there may be a published extraction procedure that you can follow.
I think that a survey of BPA concentration in household items would very interesting.
I hope this helps. Please post again if you have more questions.
A. Norman
The procedure you've outlined includes the many of the steps needed for finding the BPA concentration from UV absorption data. But there are some additions and modifications needed.
Usually the wavelength that gives maximum absorption is used for all testing. The maximum can be found by measuring the UV absorbance at several wavelengths between 200nm and 300nm. Set the spectrophotometer to the wavelength that gave the highest absorbance and leave it there for your tests.
To find the BPA concentration from UV absorbance data, you'll need to make a calibration curve. Make a stock solution of BPA in water and use it to prepare several diluted solutions of different concentrations. Measure the UV absorbance for each of the diluted solutions. Make a graph with the solution concentrations on the x-axis and absorbance on the y-axis. You can use this calibration curve to find the concentration on an unknown sample given its UV absorbance.
The following links have more details on finding the maximum wavelength and making a calibration curve:
http://www.umich.edu/~chem125/softchalk ... print.html
http://chemistry.bd.psu.edu/jircitano/beerslaw07.pdf
I'm not sure of the need for methanol in your extraction step. You might want to try placing the plastic sample in boiling (or hot) water to see if you extract any BPA. Or there may be a published extraction procedure that you can follow.
I think that a survey of BPA concentration in household items would very interesting.
I hope this helps. Please post again if you have more questions.
A. Norman