Multianion analysis, applications of ion chromatography - Determination of Anions in Natural and Treated Waters - page 648

hexavalent for tetrapolyphosphate. In Fig. 12.17, the HPIC-AS5A (5µ) column is used to
elute a large number of anions in one run. The initial eluant is weak enough to retain
fluoride well out of the void volume and separate several weakly retained monoprotic
organic acids, while the final eluant concentration is capable of eluting triprotic
phosphate and citrate. As shown in Fig. 12.17, 36 ions eluted in 30min illustrates the
power of gradient elution.
Carbon dioxide readily dissolves in basic solutions, producing carbonate. Carbonate
contamination in sodium hydroxide eluants can greatly increase the baseline shift during
a gradient run. Eluants should be prepared from 50% solutions of sodium hydroxide, as
they contain lower concentrations of carbonate than the solid. 18 meg-Ω deionised water
should be used and degassed prior to addition of sodium hydroxide. Eluants should be
maintained under an inert atmosphere during use. The Dionex Eluant Degas Module (P/N
37124) and Eluant Container Set (P/N 38752) provide a convenient method for ensuring
that the eluants are properly degassed and free from carbonate contamination. p -
Cyanophenate is a more powerful eluant than sodium hydroxide and should be used with
higher capacity separators. The HPIC-AS6 provides

Fig. 12.19 Ion chromatography of phosphorous containing anions [24]

Eluant 1: Water

Eluant 2: 100mM NaOH

1ml min −1

Flow rate: