Researcher

Matthew McBride

Objective

To determine the extinction coefficient of trans-dibenzalacetone in ethanol

Procedure

Dissolve a known amount of trans-dibenzalacetone in ethanol and calculate the extinction coefficient using UV/Vis Spectroscopy and Beer's law.

Results

Lambda 2 UV/Spectrometer Results
Spreadsheet with results
λ max: 329 nm
Absorption units at λ max (A): 0.755 (corrected for baseline)
Pathlength (L): 1 cm
Concentration (c): 2.121e-5 M
Calculated extinction coefficient (ε) of trans-dibenzalacetone in ethanol using Beer's Law (A=εLc): 35596

Lambda 35 UV/Spectrometer Results
UV/Vis Spectrum
λ max: 327 nm
Absorption units at λ max (A): 0.756606 (cannot look at spectrum to obtain this number, but must look at .jdx file directly)
Pathlength (L): 1 cm
Concentration (c): 2.121e-5 M
Calculated extinction coefficient (ε) of trans-dibenzalacetone in ethanol using Beer's Law (A=εLc): 35667

Discussion

Both spectrometers provided the same value and this is similar to the value that was found in literature.

Conclusion

The extinction coefficient of trans-dibenzalacetone in ethanol is about 35000

Log

2012-08-07

15:35 Added 0.0497 g of trans-dibenzalacetone (Product 284A from UCEXP284) to a 10 mL volumetric flask.
15:47 The flask was filled with ethanol and the crystals were dissolved into the solution. This was a 0.0212128 M solution and Solution A.
15:50 1 mL of Solution A was transferred to a 10 mL volumetric flask and the flask was filled with ethanol to create Solution A_10dilution. The solution was inverted to mix and each flask was washed 3x prior to use. 1 mL of Solution A_10dilution was transferred to a 10 mL volumetric flask and filled with ethanol to create Solution A_100dilution. The solution was inverted to mix. 1 mL of Solution A_100dilution was transferred to a 10 mL volumetric flask and filled with ethanol to create Solution A_1000dilution. The solution was inverted to mix. A 1 cm pathlength cuvette was filled with Solution A_1000dilution and another cuvette was filled with ethanol. The sample was analyzed in dual beam mode using the Lambda 2 UV/Vis Spectrometer by manually selecting wavelengths and then the absorbance at each wavelength was recorded. The sample was also analyzed in dual beam mode using the Lambda 35 UV/Vis Spectrometer and the spectrum of the file was saved as ONSEXP333A_1000dilution.