Chemistry Reference
In-Depth Information
Apparatus
Dionex Auto Ion System 12 Analyzer (Dionex Corp., Sunnyvale, California) consisting
of a Model 12 ion chromatograph (Dionex Corp.) coupled with a Gilson autosampler, a
Columbia Scientific Industries Supergrator 3-A integrator and a Gilford Instrument
Laboratories dual pen strip chart recorder. A concentrator/precolumn (4×50mm, Dionex
30825) and separator column (4×250mm, Dionex 30827) were used for the standard
seven anion determination. Two anion concentrator precolumns (4×50mm Dionex
30825) connected in series (fast run series) were employed for the five anion analyses. A
high capacity suppressor column (9×100mm Dionex 30828) containing a strong acid
cation exchange resin in the hydrogen form was used for all chromatography. The ion
chromatograph was equipped with a 250pL sample loop. A conductivity full scale
sensitivity setting of 30µmho was routinely used.
Eluent pump flow rate of 35-40% (161-184ml h
−1
) maintained system pressure
between 500 and 700psi. Both the sample and regeneration pumps were operated at 50%
flow rate (230ml h
−1
).
Procedure
Filter 10ml of sample through a 0.22µm membrane and collect the filtrate in a 15ml
capacity polystyrene vial containing 100µL of 1+1 sodium bicarbonate/sodium carbonate
solution. Calibration was established initially and after every six sample analyses by
using the combination anion solution indicated in Table 12.26. The calibration standard
were prepared fresh daily from separate 1000mg L
−1
stock solutions, fortified in the same
manner as the samples with bicarbonate/carbonate solution.
Analysis time per run (seven anion determination) was about 24min. Table 12.27
contains information on the calibrated range of the automated method.
Table 12.26
Typical retention times and peak heights of the calibration standard
Concn. mg L
−1
Anion
Approx retention time,
min
Approx peak height
µV
5.0 fluoride (F)
2.1
54,000
5.0 chloride (Cl)
3.5
30,000
20.0 nitrite (NO
2
)
4.5
50,000
25.0 orthophosphate
(PO
4
)
7.0
24,000
25.0 bromide (Br)
9.0
24,300
5.0
nitrate (NO
3
)
11.0
5,000
50.0 sulphate (SO
4
)
15.5
50,700
Source: Reproduced with permission from the American Chemical Society [78]
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