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Spectrotitration of ethane-1-hydroxy-1,1-diphosphonic acid (EHDP(tm)) with thorium diaminocyclohexanetetra-acetate.

Authors
  • Liggett, S J1
  • Libby, R A
  • 1 Miami Valley Laboratories Procter and Gamble Co. Cincinnati, Ohio 45239. U.S.A.
Type
Published Article
Journal
Talanta
Publisher
Elsevier
Publication Date
Nov 01, 1970
Volume
17
Issue
11
Pages
1135–1140
Identifiers
PMID: 18960842
Source
Medline
License
Unknown

Abstract

An automatic spectrotitration procedure for EHDP has been developed. It is applicable to samples containing 50mug or more of EHDP, with a relative standard deviation of 3% if no interfering materials are present. The sensitivity can be extended down to about 5mug, but titration blanks become significant and the standard deviation increases markedly. Thorium diaminocyclohexanetetra-acetate (Th-DCTA) is used as the titrant, to give a ternary species (Th-DCTA)(2)-EHDP. The end-point in the spectrotitration is due to deprotonation of Xylenol Orange indicator when it is incorporated into a weaker ternary species after all the EHDP has reacted. Salts such as NaCl, NaClO(4), Na(2)SO(4) and NaNO(3) interfere if present at concentrations of 0.1-0.5M. The method is much more sensitive to orthophosphate, but this interference can be averted by isolating the EHDP before titration by selectively adsorbing the phosphonate on calcium hydroxyapatite.

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