Chemistry Reference
In-Depth Information
o-Phosphate-P
9.0
7.5
0.061
Nitrate-N
11.3
9.4
0.013
Sulphate
21.4
17.8
0.206
Standard conditions:
Columns—as specified [29]; Detector—as specified [29]; Eluent—as specified [29]
Sample loop 100µL; Pump volume 2.30ml min
−1
1
Concentrations of mixed standard (mg L
−1
)
Fluoride 3.0; Chloride 4.0; Nitrite-N 10.0; O-Phosphate-P 9.0; Nitrate-N 30.0; Sulphate 50.0
2
MDL calculated from data obtained using an attenuator setting of 1 µMHO full scale. Other
settings would produce an MDL proportional to their value
Source: Reproduced with permission from the Environmental Protection Agency, US [16]
Cyanide, sulphide, iodide and bromide
Rocklin and Johnson [18] used an electrochemical detector in the ion chromatographic
determination of cyanide and sulphide. They showed that by placing an ion exchange
column in front of an electrochemical detector, using a silver working electrode, they
were able to separate cyanide, sulphide, iodide and bromide and detect them in water
samples at concentrations of 2, 30, 10 and 10µg L
−1
respectively. Cyanide and sulphide
could be determined simultaneously. The method has been applied to the analysis of
complexed cyanides and it is shown that cadmium and zinc cyanides can be determined
as total free cyanide while nickel and copper complexes can only partially be determined
in this way. The strongly bound cyanide in gold, iron or cobalt complexes cannot be
determined by this method.
This method is based on the work of Pihlar and Kosta [19,20] who showed that a silver
working electrode has the ability to produce a current that is linearly proportional to the
concentration of cyanide in an amperometric electrochemical flow through cell. The
reaction for cyanide is:
Under these conditions sulphides and halides produce insoluble precipitates rather than
soluble complexes:
Table 12.6
Single-operator accuracy and precision
Sample
type
Spike
(mg
L
−1
)
No. of
replicates %
Mean recovery
(mg L
−1
)
Standard
deviation
Analyte
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