Multianion analysis, applications of ion chromatography - Determination of Anions in Natural and Treated Waters - page 633

described in detail. With sample preconcentration detection limits were reduced to about
5µg L −1 but calibration graphs for chloride and nitrate were not linear. Sodium adipate
and 1.4×10 −3 M disodium succinate are used as eluants, both at pH 7.
On Zipax SAX the ions are eluted in the order
Fluoride is eluted together with the negative water peak. On
Zipax SAX the optimal eluent temperature for obtaining good resolution in the minimal
time is about 25°C.
Tong and Shi [15] used ion chromatography with an electrical conductivity detector to
determine fluoride, chloride, nitrate, sulphate and hydrogen phosphate (HPO 4 2− ) in non
saline water with detection limits of 0.8, 1.0, 8.0, 10.0 and 12.5µg L −1 respectively.
The Environmental Protection Agency has issued a standard ion chromatographic
method for the determination of chloride, fluoride, nitrate, nitrite, orthophosphate and
sulphate in non saline waters [16,56]. This is an approved method for the determination
of chloride, nitrate and sulphate. In this method a 2-3ml sample is introduced into the ion
chromatograph. The anions are separated and measured using a system comprised of a
guard column, separator column, suppressor column and conductivity detector.

Ground column 4×50mm Dionex P/N 030825
Separator column 4×250mm Dionex P/N 030827
Suppressor coulmn, fibre Dionex P/N 35350
Detector, conductivity cell approx 6µL

Volume, an eluent comprising sodium bicarbonate (0.003M), sodium carbonate
(0.0024M) is used.
Samples are collected in clean glass or polyethylene bottles and must be analysed
within 28d (chloride and fluoride, 48h (nitrate, nitrite and phosphate) and 28d (sulphate).
Table 12.5 lists the analysis conditions required and detection limits achieved in this
method. Recovery and accuracy are listed in Table 12.6.
Wilken and Kock [17] have described a method for the determination of chloride,
nitrate and sulphate in sediment pore waters. Depth versus concentration profiles are
reproduced for each of these ions and differences between those for the inner estuary, the
mixing zone and the outer estuary are commented on . The method was particularly useful
as it permitted the simultaneous determination of the three ions in samples of only
100µL, unaffected by the natural colour of the sample.

Table 12.5 Chromatographic conditions and method detection limits in reagent water

Retention 1 time
(min)

Method 2 detection limit mg
L −1

Relative retention
time Analyte

Fluoride 1.2 1.0 0.005

Chloride 3.4 2.8 0.015

Nitrite-N 4.5 3.8 0.004