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 Indicator	Color change	pH range	Metals detected
Mordant black II Eriochrome black T Solochrome black T	Red to blue	6 - 7	Ca, Ba, Mg, Zn, Cd, Mn, Pb, Hg
Murexide (Ammonium purpurate)	Violet to blue	12	Ca, Cu, Co
Catechol-violet	Violet to red	8 to 10	Mn, Mg, Fe, Co, Pb
Methyl blue	Blue to yellow	4 to 5	Pb, Zn, Cd, Hg
Thymol blue	Blue to grey	10 to 12	Pb, Zn, Cd, Hg
Alizarin	Red to yellow	4.3	Pb, Zn, Co, Mg, Cu
Sodium alizarin sulphonate	Blue to red	4	Al, Thorium
Xylenol orange	Lemon to yellow	1 to 3 4 to 5 5 to 6	Bi, Thorium Pb, Zn Cd, Hg

Masking agents

Masking agent	pH	Ions masked	Ions titrated with EDTA
Cyanide	10	Cu, Co, Ni, Zn, Cd, Hg, Pt, Pd, Ag, Fe	Pb, Mn, Mg, Ca, alkaline earths, rare earths
Triethanolamine	10	Sn, Al, Fe	Zn, Cd, Pb, Mn, rare earths
Aluminium Fluoride	10 6	Al, alkaline earths, rare earths Al, Ti	Zn, Cd, Mn Cu
Ascorbic acid	2	Cu, Fe, Hg	Bi, Th
Ammonia	10	Zn	Cd

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


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