usually in calculating first and second order kinetics, we use the value of concentration. but if i want to calculate the reaction kinetics by using using flourescence intensity, what will be the equation?
Hi Parvin,
First try to plot graph between solution concentration and fluorescence intensity if you get linear correlation and see over what concentration range you have linear correlation.
Second use fluorescence intensity values in that range of concentration as usual in first or second order integrated rate law expressions and do your plots and calculation. Good Luck.
I agree with Salim Y Hanna. Often Fluorescence intensity (FI) is proportional to concentration and substituting FI for concentration will work however it gets much more complicated if you are in a region where FI is not proportional to concentration. I have attached an article that could help if you find yourself in a region where FI vs concentration is not linear. Wikepdia also has a reasonable description of how this works
https://www.thermofisher.com/us/en/home/references/molecular-probes-the-handbook/introduction-to-fluorescence-techniques.html
I did one work on "photodegradation of textile wastewater using one nano catalyst. here measured the DOM degradation using flourescent spectrometry. so i get the results in Raman unit. so my qustion is, is it possible to drew reaction kinetics with the raman unit?
Hi Parvin,
Yes it is possible.You can use any units intensity , absorbance, transmission or area or....etc. As long you are in the region of linear proportion.
If fluorescence intensity linearly depends on the conversion degree of reaction, then this is possible. However, you must remember that in the case of the first order reaction with the kinetic equation: r = kcA, the degree of conversion does not depend on the initial concentration of the substrate A, but in the case of the second order reaction with the kinetic equations: r = kcA2,r r = kcAcB etc. depends. You do not know, however, before the experiment, what the reaction order is, and therefore you need to perform the experiment with several initial substrate concentrations.
Of course, there will be no problem linking the intensity of fluorescence to the conversion degree for reaction A -> B. The value of the reaction rate constant will be different from that based on concentration measurement. Difficulties may occur, however, with bimolecular reaction and then better measure the concentration.
And finally, I intetionally used the term reaction order instead of kinetic order because this is correct.
Regards,
What will be the unit of k in pseudo second order kinetic, when we draw it by using flouresence intensity instead of concentration? Mirosław Grzesik ?
You are worried about the unit of reaction rate constant? There is no problem: first order reaction of 1 /s, second order reaction of m3 / (mol s) (of course, instead of "mole" will be the intensity of fluorescence). The problem is something else. In suspicion you we are dealing with a second order reaction, you should perform an experiment for several initial molar ratios of substrates (A + B => P) and for several initial substrate concentrations (A => P).) You also need to define the conversion, so you need the value of nitial intensity (or final in case if it is equal to zero)..
Finally the question: what is the source of fluorescence. No problem if the product or one of the substrates. Worse, if both.
And one more thing. In this case, the term "pseudo" is not justified.
Regards,
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