I'm working since several months with a solution of Fluorescein Disodium (C20H10Na2O5) and Ethanol. So far, the spectrum of this solution is changing due to unknown parameters and I would like to fix some of them.
In literature they say that Fluorescein in Water solution has problem because it change the pH and to make it constant they add Sodium Hydroxyde or Disodium hydrogen phosphate and potassium dihydrogen phosphate. @Shafii and @Chaze. I do not have advanced knowledge of chemistry so could someone help me to choose how to fix the pH of my solution adding a salt in ethanol?
The experiments I'm doing is a bit more complex than using only Fluorescein as temperature tracer: I actually use the combination FL/Kiton Red (sulforodhamine-C27H29N2NaO7S2). What I observed is that after preparing a new solution with fixed concentrations of both dyes, I stored it in darkness and at 16 deg. I take samples from this solution and day by day the sensitivity in temperature is changing. I'm using the wavelenght band 540-550 integral and 575-590 nm.
Since Fluorescein and Kiton Red have quite well separated wavelenght bands of emission, from observations of the single temeprature dependence it seems that Fluorescein dependence is dramatically decreasing while Kiton Red is slightly changing ( its temperature dependence is actually increasing most probably due to the tail of fluorescein emission which is becoming more and more small). Could someone with experience in fluorescent solutions be available to have a chat about it?
Thanks!
I have often used fluorescein or rhodamine with a fluorometer to measure concentration (or rather, dilution). Temperature is perhaps the smallest variable in this process. Uncertainties in the other variables (including time) will likely overwhelm your indication of temperature. I don't know how you could possibly control the other variables so as to effectively use the temperature response as a measurement. Why are you taking this approach? Are there no other means? Optically reactive paint works fairly well to get a rough estimate of temperature, but it's not accurate. A fluorometer is not accurate on an absolute scale, but it is repeatable and fairly linear over a limited range of concentrations. This means that the results can be accurately inferred from calibration solutions. Also, salts don't work well with alcohols. Consider molecules that are organic on one end and inorganic on the other.
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