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Fluorescein

Exploratory experiments

The goal is to evaluate the concentration required to have an absorbance of around 0.5

We took 14 mg of fluorescein in 100mL of water

14 mg/L

ColorAbsorbanceEmission
Red0.01
Green0.43
Blue1.79
UV-1358

From the previous solution we 0.5mL and bring it to 5mL.

1.4 mg/L

ColorAbsorbanceEmission
Red-0.02
Green0.14
Blue0.95
UV-2878

0.7 mg/L

ColorAbsorbanceEmission
Red0
Green0.07
Blue0.56
UV2953

Exploratory Conclusions

An absorbance in blue of around 0.5 is achieved with a concentration of phenolphathlein of 0.7mg/L.

At this concentration the spectrophotometer has a fluorescence of 2953 internal unit.

CaCl2.2H2O solution

4.64 g/L

Fluorescence in presence of Ca++

Solution A: fluorescein 1.4 mg/L Solution B: CaCl2.H2O 4.64 g/L

ABH2ORGBUV
202-0.010.100.532237
20.51.5-0.010.110.552160
21100.100.552193
21.50.5-0.000.110.552265
2200.000.100.552250

369mg of CaCl2.2H2O in 2 + 2 mL (2 experiments) (concentration of 92g/L)

ABH2ORGBUV
202-0.000.090.522052
202-0.000.110.532088

Conclusion

In presence of CaCl2 at high concentration there is no clear evidence of a fluorescence quenching.

Test with KI

Solution A: fluoresceine 1.4 mg/L Solution B: KI 10 g/L

ABH2ORGBUVUV second experiment
20200.070.5629532942
20.51.50.010.070.5828172816
2110.000.080.5626032618
21.50.50.000.070.5725032517
22000.070.5722832243

All data

Conclusions

It seems that we observe a fluorescence quenching but other factors like influence of pH should be checked. Literature shows that this kind of experiment is done in presence of 0.1M of KOH.

Check page 12 of : Fluoroscence - Quenching