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

Solution A_100,000 UV/Vis Spectrum
λ max: 328 nm
Absorption units at λ max (A): 0.015550
Pathlength (L): 1 cm
Concentration (c): 9.3046e-8 M
Calculated extinction coefficient (ε) using Beer's Law (A=εLc): 167121

Solution A_10,000 UV/Vis Spectrum
λ max: 329 nm
Absorption units at λ max (A): 0.120824
Pathlength (L): 1 cm
Concentration (c): 9.3046e-7 M
Calculated extinction coefficient (ε) using Beer's Law (A=εLc): 129854

Solution B_10,000 UV/Vis Spectrum
λ max: 330 nm
Absorption units at λ max (A): 0.580883
Pathlength (L): 1 cm
Concentration (c): 9.3046e-7 M
Calculated extinction coefficient (ε) using Beer's Law (A=εLc): 624296

Discussion

Calculated values are not consistant and high

Conclusion

No reliable extinction coefficient could be determined.

Log

2012-07-31

16:23 Added 0.0109 g of trans-dibenzalacetone (Product 284A from UCEXP284) to a 5-dram snap cap vial.
16:28 Added approximately 2-3 mL of ethanol to the vial and dissolved the crystals. The solution was then transferred to a 5 mL volumetric flask and filled with ethanol. This was the stock solution (Solution A) with a concentration of 0.0093046M.
16:30 50 µL of Solution A was added to a 5 mL volumetric flask and filled with ethanol to create Solution A_100dilution.
16:33 50 µL of Solution A_100dilution was added to a 5 mL volumetric flask and filled with ethanol to create Solution A_10,000dilution.
16:40 1 mL of Solution A_10,000dilution was added to a 10 mL volumetric flask and filled with ethanol to create Solution A_100,000dilution. 3 mL of this solution was added to a cuvette with a 1 cm pathlength and analyzed by UV/Vis spectroscopy. The file of this spectrum was saved as ONSEXP329A_100,000dilution. The absorption units of this spectrum was 0.01.
17:00 3 mL of the Solution A_10,000 was added to a cuvette and analyzed by UV/Vis spectroscopy. The file of the spectrum was saved as ONSEXP329A_10,000. The absorption units of this spectrum was around 0.12.

2012-08-01

16:03 Inverted Solution A several times to throughly mix the solution. Added 50 µL of Solution A to a 5 mL volumetric flask and filled with ethanol. This is Solution B_100dilution. The solution was inverted several times to throughly mix.
16:11 Added 50 µL of Solution B_100dilution to a 5 mL flask and filled with ethanol. This is Solution B_10,000dilution. The solution was inverted several times to throughly mix. 3 mL of Solution B_10,000dilution was added to a cuvette with a 1 cm pathlength and analyzed by UV/Vis spectroscopy. The file of the spectrum was saved as ONSEXP329B_10,000dilution.

## 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

Solution A_100,000UV/Vis Spectrum

λ max: 328 nm

Absorption units at λ max (A): 0.015550

Pathlength (L): 1 cm

Concentration (c): 9.3046e-8 M

Calculated extinction coefficient (ε) using Beer's Law (A=εLc): 167121

Solution A_10,000UV/Vis Spectrum

λ max: 329 nm

Absorption units at λ max (A): 0.120824

Pathlength (L): 1 cm

Concentration (c): 9.3046e-7 M

Calculated extinction coefficient (ε) using Beer's Law (A=εLc): 129854

Solution B_10,000UV/Vis Spectrum

λ max: 330 nm

Absorption units at λ max (A): 0.580883

Pathlength (L): 1 cm

Concentration (c): 9.3046e-7 M

Calculated extinction coefficient (ε) using Beer's Law (A=εLc): 624296

## Discussion

Calculated values are not consistant and high## Conclusion

No reliable extinction coefficient could be determined.## Log

## 2012-07-31

16:23 Added 0.0109 g of trans-dibenzalacetone (Product 284A from UCEXP284) to a 5-dram snap cap vial.16:28 Added approximately 2-3 mL of ethanol to the vial and dissolved the crystals. The solution was then transferred to a 5 mL volumetric flask and filled with ethanol. This was the stock solution (Solution A) with a concentration of 0.0093046M.

16:30 50 µL of Solution A was added to a 5 mL volumetric flask and filled with ethanol to create Solution A_100dilution.

16:33 50 µL of Solution A_100dilution was added to a 5 mL volumetric flask and filled with ethanol to create Solution A_10,000dilution.

16:40 1 mL of Solution A_10,000dilution was added to a 10 mL volumetric flask and filled with ethanol to create Solution A_100,000dilution. 3 mL of this solution was added to a cuvette with a 1 cm pathlength and analyzed by UV/Vis spectroscopy. The file of this spectrum was saved as ONSEXP329A_100,000dilution. The absorption units of this spectrum was 0.01.

17:00 3 mL of the Solution A_10,000 was added to a cuvette and analyzed by UV/Vis spectroscopy. The file of the spectrum was saved as ONSEXP329A_10,000. The absorption units of this spectrum was around 0.12.

## 2012-08-01

16:03 Inverted Solution A several times to throughly mix the solution. Added 50 µL of Solution A to a 5 mL volumetric flask and filled with ethanol. This is Solution B_100dilution. The solution was inverted several times to throughly mix.16:11 Added 50 µL of Solution B_100dilution to a 5 mL flask and filled with ethanol. This is Solution B_10,000dilution. The solution was inverted several times to throughly mix. 3 mL of Solution B_10,000dilution was added to a cuvette with a 1 cm pathlength and analyzed by UV/Vis spectroscopy. The file of the spectrum was saved as ONSEXP329B_10,000dilution.