Chemistry Reference
In-Depth Information
separate for 10min and then remove the organic phase. Add a further 4.0ml of
chloroform, shake for 1min and repeat as above. Centrifuge the final aqueous phase at
4500g for 15min. Decant this aqueous phase into a 2.0 ml glass sample cup and aspirate,
in duplicate, at the rate of 50 per h into the Auto Analyzer used for the total iodine
method.
Prepare a calibration graph by feeding appropriate iodate-iodine standards directly to
the AntoAnalyzer. Determine the reagent blank by treating a sample of deionised,
distilled water according to the procedure above. Substract this reagent blank from the
peak height returned for each sample. Where reducing agents are present, or a new water
type is under investigation, determine the 'catalytic method' blank as discussed above.
Substract this blank from the peak height of the sample, and finally read off the iodate-
iodine concentration from the calibration graph.
T
he addition of 100mg L
−1
of S(as SO
4
2−
), HCO
3
−
, P(as PO
4
3−
), Ca
2+
, Mg
2+
, K
+
and
Na
+
, 30mg L
−1
of Cl
−
and NO
3
−
, 15mg L
−1
of Si(as SiO
3
) and Br
−
and 100µg L
−1
of
Fe
2+
, Fe
3+
, Mn
2+
and Ni
2+
did not produce any significant interference in the procedure
for the determination of iodate. In these experiments a mixture containing 3.0µg L
−1
of
iodide and 2.0µg L
−1
of iodate-iodine together with the other chemicals was analysed and
in each instance analysis gave 2.0 ± 0.1µg L
−1
of iodate-iodine. The addition of up to
10
−2
mol L
−1
of either hydrogen or hydroxyl ion to the sample prior to its analysis also
produced an insignificant interference.
2.49.2
Inductively coupled plasma atomic emission spectrometry
Miyazaki and Brancho [346] carried out a differential determination of iodate and iodide
in non saline water by solvent extraction-inductively coupled plasma atomic emission
spectrometry. Iodate was reduced to iodide, which was oxidised to iodine and extracted
into xylene. Combined extracts were introduced into the spectrometer and iodine
determined at 178.28nm. Iodine alone was detected as previously without reducing
iodate. Detection limits at 178.28nm and at 206.16nm were 8.3 and 21µg L
−1
. Large
concentrations of bromide interfered. The use of non-polar solvents would improve the
detection limits.
2.49.3
Cathodic stripping voltammetry
The application of this technique is discussed under multianion analysis in section
14.9.1.2.
2.49.4
Polarography
The application of this technique is discussed under multianion analysis in section
14.10.1.1.
2.49.5
Ion selective electrodes
The determination of iodate and iodide has been carried out using an iodide selective
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