Chemistry Reference
In-Depth Information
reporting limit of 0.2mg L−1
n
itrate was a pre-established requirement for the automated
ion chromatographic method. The concentration of nitrate used to establish calibration
had to possess a retention time with a 10% window that encompassed the retention time
of a 0.2mg L
−1
nitrate peak. Calibration with a 5.0mg L−1 nitrate standard provided a
reasonable compromise whereby the widest dynamic range in which identification of the
required minimum reporting limit (0.2mgL
−1
nitrate) was attainable. With this
concentration of nitrate used for calibration the range of the method was 0.2-30mg L
−1
nitrate. Concentrations of nitrate >30mg L−1
ni
trate resulted in retention times outside the
10% window and were identified by the integrator as extraneous peaks or sometimes
incorrectly as bromide (anion eluting immediately before nitrate).
Table 12.28
Change in retention time with concentration of nitrate
Retention time normalised to 5.0mg L−1 NO
3
,
min
Nitrate, mg
L−1
Retention time,
min
0.2
12.4
+1.2
5.0
11.2
0
20.0
10.9
−0.3
25.0
10.9
−0.3
45.0
9.2
−2.0
Source: Reproduced with permission from the American Chemical Society [78]
Table 12.29
Comparison of results (mg L
−1
) obtained with automated ion
chromatography vs results obtained with traditional methods
Water
type
Fluoride
(F)
Chloride
(Cl)
Nitrite
(NO
2
)
Orthophosphate
(PO
4
)
Brom
(Br)
1C
Electrode 1C
Wet
chem
1C
Wet
chem
1C
Wet
chem
1C
0.1
16
16
<0.5
<0.2
<0.05 0.5
Boiler
feed
Boiler
0.2
1.2
1.5
<0.5
11
9.9
<0.5
Boiler
1.2
140
125
<5
14
14.4 <0.5
Cooling 4.0
20
24
<0.5
2.0
2.5
1.4
Cooling 0.4
23
28
<0.5
4.2
4.2
<0.5
Zeolite
softened
0.1
18
18
<0.5
<0.2
<0.05 <0.5
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