Chemistry Reference
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AS5A-5µ provides an impressive profile of inorganic ions and organic acid anions from
a single injection of sample (Fig 2.12). Note that phosphate and citrate, strongly retained
trivalent ions, are efficiently eluted in the same run that also gives baseline resolution of
the weakly retained monovalents fluoride, acetate, formate and pyruvate. Quantitation of
all the analytes shown in Fig. 2.12 using conventional columns would require at least
three injections under different eluent conditions.
Another benefit of using the AS5A-5µ gradient pump combination is the ability to
change easily the order of elution of ions with different valencies simply by changing the
gradient profile. For example, if nitrate were present in high enough concentration to
interfere with a malate peak, the malate peak could be moved ahead of the nitrate peak by
using a slightly different gradient (Fig 2.12c).
2.15.2
Column chromatography
Liquid chromatography separation and indirect detection using iron(II), 1,10-
phenanthroline as a mobile phase additive have been used for the separation of
carboxylates (and sulphonic acids) [161]. Detection limits approach 20ng.
2.15.3
Ion exclusion chromatography
Okada [162] has described a redox suppression for the ion exclusion chromatography of
carboxylic acids with conductiometric detection. The reaction between hydriodic acid
(the eluant) and hydrogen peroxide (the precolumn reagent) is used as the redox
suppressor for ion exclusion chromatography of carboxylic acids. The suppressor is
useful with highly acidic eluents and reduces background conductance more effectively
than a conventional ion exchange suppressor.
2.15.4
Gas chromatography
The application of this technique is discussed under multianion analysis in section
14.1.1.1.
2.15.5
Miscellaneous
The determination of carboxylic acids is also discussed in the following sections:
Ion chromatography (sections 2.1, 2.3, 2.13, 2.18, 2.20, 2.21, 2.26, 2.27, 2.33-2.36,
2.38-2.41, 2.44-2.46, 2.51-2.56, 2.60, 2.71, 2.74, 2.79, 2.80, 2.84, 2.86, 2.87, 2.92,
2.104, 2.108).
High performance liquid chromatography (sections 2.1, 2.13, 2.26, 2.40, 2.45, 2.51,
2.54, 2.72, 2.80, 2.82).
Micelle chromatography (section 2.51).
Ion exclusion chromatography (sections 2.21, 2.34, 2.40, 2.55. 2.56, 2.97).
Gas chromatography (sections 2.42, 2.56).
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