Multianion analysis, applications of ion chromatography - Determination of Anions in Natural and Treated Waters - page 677

Table 12.22 Instrumental conditions

Instruments Dionex model 20 1 0i ion chromatograph

Dionex electrochemical detector
Houston Instrument Omniscribe chart recorder

Electrochemical applied
potential

0.4V

0.25cm min −1

Chart recorder speed

1.5ml min −1

Flow rate

Suppressor column Dionex AMS, preproduction prototype,

Membrane suppressor

Injection volume 0.1 0ml

0.0016mol L −1 , Li 2 CO 3 +0.0024mol L −1 LiCOOH.H 2 O
pH=10.4 Monovalent cations and anions

Eluant

Separator columns

Anion separator 150×4mm id Dionex HPIC-AS3 anion

Cation separator 200×4mm id Dionex HPIC-CSI cation

0.0033mol L −1 Cu phthalate divalent cations and anions

Eluant
Separator columns

Anion separator 250×4.6mm id Vydac 3021C4.6 anion

Cation separator 200×4mm id Dionex HPIC-CSI cation

Source: Reproduced with permission from International Scientific Communications Inc [63]

a basic pH, it is possible to separate simultaneously and detect the monovalent cations
(with the exception of the ammonium ion) and anions, while an eluant with an acidic pH
allows for the separation and detection of divalent cations and anions.
The equipment and operating conditions used by Jones and Tarter [63] are described
below. The instrumental set-up consists primarily of two separator columns, two
detectors and one suppressor column. The analyte flows through the injection valve into
the cation separator, where the cations are separated. The separated cations are then
detected using a conductivity detector (this is, in effect, a single column ion
chromatographic analysis at this stage). The anions, which are essentially unretained on
the cation column, are separated on the anion separator column. The ions then travel
through the anion suppressor column, where the previously separated and detected
cations are removed. Finally, the separated anions pass through the second detector,
which may be a conductivity detector or an electrochemical detector. The electrochemical
detector responds to pH changes in the eluant as the dissociated acids pass through the
detector.