Chemistry Reference
In-Depth Information
a
Measured on unfiltered sample at 400nm; A=absorbance units
b
No correction at 275nm was applied to the manual method
c
Calibration range 0-25µg mL
−1
of N
Source: Reproduced with permission from the Royal Society of Chemistry [49]
of this matter through the membrane was significantly lower than that of nitrate ions. The
nitrate concentrations of three highly coloured raw Pennine waters were determined by
the conventional continuous-flow reduction method [51]. the manual nitrate method [52]
(using unfiltered samples), and the above dialysis method. The results (Table 7.14) show
that the dialysis method eliminates the ultraviolet absorption contribution from organic
matter observed with the manual method and that there is good agreement between the
dialysis method and the continuous-flow
Table 7.15
Effect of other substances on nitrate. If other substances did not interfere, the
results would be expected (95% confidence) to be in the following ranges:
10.00 ± 0.33µg mL
−1
and 0.00 ± 0.05µg mL
−1
. Negligible interference was
observed from the presence of Ca (200µg mL
−1
), Mg (100µg mL
−1
), K (200µg
mL
−1
) and NH
4
, (1 00µg mL
−1
N0, all present as chlorides
Concn
mg L
−1
Added as
mg L
−1
Measured nitrate concentration
a
of N
Substance
Cl
1000 NaCl
10.19
0.02
SO
4
1000 Na
2
SO
4
10.09
0.00
PO
4
(as P)
5 KH
2
PO
4
9.74
0.01
F
5 NaF
9.70
0.00
Humic acid
250 -
10.15
0.33
Fulvic acid
250 -
11.58
1.36
10 FeSO
4
Fe(II)
10.27
0.06
10
FeCl
3
Fe(III)
9.89
0.00
NO
2
(as N)
50
NaNO
2
10.01
0.00
10 K
2
Cr
2
O
7
Cr(VI)
9.85
0.13
Persil
b
10 -
9.76
0.00
2
Al
2
(SO4)
3
Al
9.92
0.00
2
MnSO
4
Mn
10.03
0.02
I
5 KI
10.17
0.00
Br
5 KBr
9.98
0.00
Glucose
100 -
10.25
0.00
Acetate
100 CH3COONa
10.25
0.00
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