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
Color | Absorbance | Emission |
---|---|---|
Red | 0.01 | |
Green | 0.43 | |
Blue | 1.79 | |
UV | -1358 |
From the previous solution we 0.5mL and bring it to 5mL.
1.4 mg/L
Color | Absorbance | Emission |
---|---|---|
Red | -0.02 | |
Green | 0.14 | |
Blue | 0.95 | |
UV | -2878 |
0.7 mg/L
Color | Absorbance | Emission |
---|---|---|
Red | 0 | |
Green | 0.07 | |
Blue | 0.56 | |
UV | 2953 |
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
A | B | H2O | R | G | B | UV |
---|---|---|---|---|---|---|
2 | 0 | 2 | -0.01 | 0.10 | 0.53 | 2237 |
2 | 0.5 | 1.5 | -0.01 | 0.11 | 0.55 | 2160 |
2 | 1 | 1 | 0 | 0.10 | 0.55 | 2193 |
2 | 1.5 | 0.5 | -0.00 | 0.11 | 0.55 | 2265 |
2 | 2 | 0 | 0.00 | 0.10 | 0.55 | 2250 |
369mg of CaCl2.2H2O in 2 + 2 mL (2 experiments) (concentration of 92g/L)
A | B | H2O | R | G | B | UV |
---|---|---|---|---|---|---|
2 | 0 | 2 | -0.00 | 0.09 | 0.52 | 2052 |
2 | 0 | 2 | -0.00 | 0.11 | 0.53 | 2088 |
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
A | B | H2O | R | G | B | UV | UV second experiment |
---|---|---|---|---|---|---|---|
2 | 0 | 2 | 0 | 0.07 | 0.56 | 2953 | 2942 |
2 | 0.5 | 1.5 | 0.01 | 0.07 | 0.58 | 2817 | 2816 |
2 | 1 | 1 | 0.00 | 0.08 | 0.56 | 2603 | 2618 |
2 | 1.5 | 0.5 | 0.00 | 0.07 | 0.57 | 2503 | 2517 |
2 | 2 | 0 | 0 | 0.07 | 0.57 | 2283 | 2243 |
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