Learn the procedure for making a calcein indicator solution.
The compound that changes color when exposed to acidic or basic solutions is called an indicator. Most of the time, color indicators are used to measure pH. To find the endpoint or equivalence point of the titration, they are added to the reaction mixture.
Calcein (C30H26N2O13), which is also called fluorexon or fluorescein complex, is a fluorescent dye with wavelengths of 495 and 515 nm for excitation and emission, respectively. It is used as a complexometric indicator for the titration of calcium ions with EDTA and fluorometric determination of calcium.
Calcein is a fluorescent metal indicator, chemically described as 2, 7 Bis[bis(carboxymethyl)aminomethyl]fluorescein. Calcein comes in the form of a yellowish-orange powder that is slightly soluble in water.
In acidic conditions, a calcein solution emits a yellowish-green fluorescence, whereas there is no fluorescence in basic conditions. However, under basic conditions, Calcein will emit fluorescence in the presence of metal ions such as Al, Ba, Ca, Cu, Mg, and Zn.
How to prepare calcein indicator mixture for titration:
To make a fine powder that can be used as an indicator, mix 1 gram of calcein with 100 gm of potassium chloride.
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