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Masking agents and Metals determined by EDTA Titration

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Metal ion Indicators
EDTA analysis buffers

Metals detected by EDTA indicators

Metal ion indicators, masking agents and metals determined by complexation with EDTA.

Metal ion IndicatorColor changepH rangeMetals detected
Mordant black II
Eriochrome black T
Solochrome black T
Red to blue6 - 7Ca, Ba, Mg, Zn, Cd, Mn, Pb, Hg
(Ammonium purpurate)
Violet to blue12Ca, Cu, Co
Catechol-violetViolet to red8 to 10Mn, Mg, Fe, Co, Pb
Methyl blueBlue to yellow4 to 5Pb, Zn, Cd, Hg
Thymol blueBlue to grey10 to 12Pb, Zn, Cd, Hg
AlizarinRed to yellow4.3Pb, Zn, Co, Mg, Cu
Sodium alizarin sulphonateBlue to red4Al, Thorium
Xylenol orangeLemon to yellow1 to 3
4 to 5
5 to 6
Bi, Thorium
Pb, Zn
Cd, Hg

Masking agents

Masking agentpHIons maskedIons titrated with EDTA
Cyanide10Cu, Co, Ni, Zn, Cd, Hg, Pt, Pd, Ag, Fe Pb, Mn, Mg, Ca, alkaline earths, rare earths
Triethanolamine10Sn, Al, Fe Zn, Cd, Pb, Mn, rare earths
Aluminium Fluoride10
Al, alkaline earths, rare earths
Al, Ti
Zn, Cd, Mn
Ascorbic acid2Cu, Fe, Hg Bi, Th

Reference :
Dr. Asif Hussain,Jamia Hamdard, Hamdard Nagar, New Delhi- 110062
"Pharmaceutical Analysis. Theoretical Basis of Analysis: Complexometric Titrations."

Dhanlal De Lloyd, Chem. Dept, The University of The West Indies, St. Augustine campus
The Republic of Trinidad and Tobago.
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