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elutes early, near the carbonate dip. For these applications the ultraviolet detector should
be placed between the separator and suppressor columns.
13.2.1.3
Phosphate, chloride, sulphate, condensed phosphates
Ion exclusion chromatography provides a convenient way to separate molecular acids
from highly ionised substances. The separation column is packed with a cation exchange
resin in the H
+
form so that salts are converted to the corresponding acid. Ionised acids
pass rapidly through the column while molecular acids are held up to varying degrees. A
conductivity detector is commonly used.
Tanaka
et al.
[12-14] have reported that the separation of phosphate from chloride,
sulphate and several condensed phosphates P
2
O
7
4
−, P
3
O
10
2
− and P
3
O
9
3−
could be
achieved by ion exclusion chromatography on a cation exchange resin in the H+ form by
elution with an acetone water and dioxan water mixture. As the separation mechanism of
the ion exclusion chromatography by elution with water alone for numerous anions or
their respective acids is based on the Donnan membrane equilibrium principle (ion
exclusion effect) it is a highly useful technique for the separation of non-electrolytes such
as carbonic acid from electrolytes such as hydrochloric acid and sulphuric acid [15]. Ion
exclusion chromatography has also been coupled to ion chromatography to determine
simultaneously both weak and strong acids [16]. The ion exclusion chromatography
separation of orthophosphate from the strong acid anions by elution with organic solvent
water described above is based on this ion exclusion effect and/or the partition effect
between the cation exchange resin phase (water rich) and the mobile phase (organic
solvent rich) owing to the hydration of the resin [12] and phosphate has been monitored
as the corresponding acid (H
3
PO
4
) with a flow coulometric detector for the detection of
H
+
ion and a conductometric detector.
13.2.1.4
Organic anions, tartrate, maleate, malonate, citrate, glycollate,
formate and fumarate
Okada [17] employed a Redox suppressor in his ion exclusion chromatographic
determination of tartrate, maleate, malonate, citrate, glycollate, formate and fumarate in
non saline waters. A conductiometric detector was employed.
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