15 Chromogen/Metal Indicator



Metal Indicator

  • Product code
    C001  Calcein
  • CAS No.
  • Chemical name
  • MW
Unit size Price Item Code
1 g C001-10
5 g C001-12

Product Description

Calcein is a fluorescent metal indicator for calcium detection with EDTA titration. It is slightly soluble in water. The proton dissociation constants are reported to be pKa1=2.1, pKa2=2.9, pKa3=4.2, pKa4=5.5, pKa5=10.8 and pKa6=11.7. Calcein solution emits a yellowish-green fluorescence in acidic conditions, and no fluorescence in strongly basic conditions. However, Calcein will emit fluorescence in the presence of metal ions such as Al, Ba, Ca, Cu, Mg, and Zn in basic conditions. Therefore, Calcein is also used for direct fluorometric EDTA titration of these metal ions. Since Calcein has a clear endpoint even if the sample has color or contains phosphate, it is suitable for calcium detection in biological samples or fertilizers. TPC, murexide, or PPC are added to get a clear endpoint. For example, by mixing equal amounts of TPC with Calcein, intense green fluorescence will turn reddish-purple with no fluorescence at the endpoint.

Chemical Structure


Open References

1) K. Ueno, T. Imamura and K. L. Cheng, "Handbook of Organic Analitical Reagents 2nd Edition", CRC Press, 1992.
​2) R. O. Ashby and M. Roberts, "A Microdetermination of Calcium in Blood Serum", J. Lab. & Clin. Med.195749, 958. 
3) J. Korbl and F. Vydra, "Metallochromic Indicators. IV. A Note on the Preparation and Properties of Calcein", Collect. Czech. Chem. Commun.195823, 622. 
4) M. A. Demertzis, "Fluorimetric Determination of Calcium in Serum with Calcein Complexation of Calcein with Calcium and Alkali Metals", Anal. Chim. Acta, 1988209, 303. 
5) E. Muller-Ackermann, U. Panne and R. Niessner, "A Fiber Optic Sensor Array for the Fluorimetric Detection of Heavy Metals", Anal. Methods Instrum.19952(4), 182



Handling and storage condition

Appearance: Yellowish orange powder
Solubility in NaOH solution: To pass test (clear, reddish orange)
Sensitivity: To pass test
Free fluorescein: To pass test
Sulfated ash: ≦ 1.0 %
IR spectrum: Authentic
Handling and storage condition
Ambient temperature

Product Classification

Product Classification

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