Chemistry Reference
In-Depth Information
Table 8.11
Results of interference study CN
−
concentration: 0.5µg/mL
Peak area
a
Ion
Concentration Added as
(mg L
−1
)
None
100.0±2.0
F
−
500 NaF
99.2±1.7
Cl
−
500 NaCl
99.4±0.2
Br
−
500 NaBr
100.2±1.8
I
−
500 KI
98.6±1.3
SO
4
2−
500
Na
2
SO
4
100.4±3.2
NO
3
-
500
NaNO
3
100.8±2.5
HCO
3
-
500 KHCO
3
99.9±1.9
H
2
PO
4
−
500 KH
2
PO
4
99.4±0.8
SCN
−
500 NaSCN
86.0±2.1
SCN
−
100 NaSCN
99.0±3.0
CNO
−
500 KCNO
104.1±0.7
CNO
−
100 KCNO
102.8±1.7
S
2-
0.1
Na
2
S.9H
2
O
90.9±4.6
S
2-
0.05
Na
2
S.9H
2
O
100.2±2.3
NH
4
+
500 (NH
4
)
2
SO
4
101.8±1.7
a
Mean±S.D. of five replicate analyses
Source: Reproduced with permission from Elsevier Science [42]
by flame thermionic gas chromatography. In the derivatisation reaction, aqueous cyanide
reacts with aniline and sodium nitrite in the presence of copper(II) sulphate and forms
benzonitrile.
Funazo
et al.
[42] tested this method in the presence of several ions normally found in
environmental samples (Table 8.11). The peak area of benzonitrile derivatised from the
standard cyanide solution (0.5mg L
−1
) was arbitrarily assigned a value of 100.
None of the ions except thiocyanate, cyanate and sulphide interfered at a concentration
of 500mg L
−1
. At this concentration, thiocyanate interferes negatively and cyanate
positively. However, these interferences are not observed at the 100mg L
−1
level.
Sulphide ion interferes at relatively low concentrations, even at 0.1mg L
−1
, a negative
interference is observed. Similar interferences of sulphide are well known in the pyridine
pyrazolone method and in the method using a cyanide ion selective electrode. However,
sulphide can be removed from the sample solution by treating the alkaline sample at pH
11.0 with small amounts of powdered lead carbonate.
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