CHELATING RADIOMETRIC TITRATIONS BY ION EXCHANGE FOR DETERMINATION OF TRACES OF METALS. THE DATA IS TAKEN FROM RESEARCH ARTICLE. IF ARTICLE IS NEEDED, JUST WRITE IT DOWN

1. CHELATING RADIOMETRIC
TITRATIONS BY ION EXCHANGE
FOR DETERMINATION OFTRACES
OF METALS
By
Aneesa Zafar
Roll no 56

2. Some BasicTerms
• Titration and its elements
• RadiometricTitration
• Types Of RMT
I. Titration based upon Precipitate Formation
II. Titration based upon Complex Formation
III. Titration based upon Redox Reaction
IV.Titration in Non-aqueous Media

3. Precipitation titrations
• the second phase is a precipitate,
• the end-point can be determined
by the appearance of the activity in
the aqueous phase, or by its
disappearance from the aqueous
phase,
• Precipitation titrations are difficult
to apply, because of necessity for
handling precipitates, to less than
milligram amounts, impossible at
the submicrogram level.
Complexometric titrations
• formation of metal chelates which
can be separated from the
unreacted metal ions by solvent
extraction.
• The end-point is determined
similarly from the change in
activity either of the aqueous
phase or of the organic phase.
• far more sensitive, but has been
applied only to a limited number of
determinations.

4. RADIOMETRICTITRATIONS USING EDTA
• EDTA titrations are widely used for determination of many metals.
• Determination of submicrogram amounts of metals
• Formation of negatively charged or neutral chelates which can easily be
separated from the excess of the unreacted metal ions on a cation
exchanger.
• The end-point is determined from the activities of the eluates obtained.
• In radiometric titration, isotopic and non-isotopic tracer can be used.
• the determination of metals forming very stable chelates (e.g., Co (III), Zr
(IV) , Fe(lI), In(IIl),Th (IV), etc.) can be carried out at pH 2-3 using 10^-6 to
10^-7M EDTA solutions.

5. DETERMINATION OFTRACES OF INDIUM USING
ISOTOPICTRACER
Procedure:
• The pH of a series of equal, known volumes of analysed solution of indium
(2.0 ml containing about 1 µg/ml), labelled with a known amount of radio-
indium (t(1/2) = 50 days), is adjusted approximately to a value of 2-3.
• Any iron (III) present, which can interfere, is reduced to iron(II) by adding 2
drops of 10% ascorbic acid.
• The solutions thus prepared are carefully mixed with known, increasing
amounts of titrating solution (lO+M EDTA) and are simultaneously passed
through a series of cation-exchanger columns.
• Each value of activity measured represents a point on the titration curve

7. Curve Indium Added
(µg)
Radioindium
added (µg)
Total Indium
present (µg)
Total Indium
found (µg)
A 0.00 1.02 1.02 1.00
B 0.22 1.02 1.24 1.23
C 0.44 1.02 1.46 1.46
D 0.88 1.02 1.90 1.94
Traces of indium uni- and bivalent metal cations will not interfere, because of
their lower stability constants.This has been verified in the present work.
However, titrations using isotopic tracers are limited to instances where suitable
radioisotopes are available.

8. DETERMINATION OFTRACES OF COBALT
USING NON-ISOTOPICTRACER
• Because of much higher stability with EDTA of the cobalt (lI) complex than of the indium
complex it is possible to use radio-indium as non-isotopic tracer for the determination of
traces of cobalt.
• Procedure:
• To the series of solutions containing equal, known volumes of the analysed solution
(slightly acid), known, increasing amounts of EDTA (10^-5 M) are added.
• Each of these solutions is carefully mixed in a polyethylene flask with 0.5 ml of 0.0lM
aqueous ammonia containing 1.5% hydrogen peroxide.
• The pH of the solutions thus prepared should be 6-8.
• The solutions are heated on a boiling water bath for 5 min (formation of Co(III)--EDTA
complex).
• After cooling to room temperature the pH of all the solutions is readjusted to
approximately 2-3, and the radio-indium tracer is added.The remainder of the
procedure is carried out as before.

10. Curve Cobalt Added(µg) Cobalt found (µg)
A 0.00 0.00
B 0.29 0.27
C 0.58 0.56
The non-isotopic tracer most suitable for achieving the highest selectivity can also
be chosen using the stability constants of the EDTA complexes.The stability
constant of the EDTA complex of the tracer must be lower than that of the metal to
be determined, but higher than the stability constants of interfering metals which
might be present. Compared with extractive titrations, radiometric titrations using
EDTA have the advantage of high stability of the titrant even in very dilute
solutions.