Multianion analysis, miscellaneous methods - Determination of Anions in Natural and Treated Waters - page 721

4.74 4.76 - 0.02 100.4

4.74 4.76 100.0 0.02 100.4

1.26 1.14 - −0.12 90.5

1.26 1.13 50.0 −0.13 89.7

0.625 0.565 - 0.06 90.4

0.625 0.578 50.0 −0.047 92.2

0.252 0.241 - 0.0 11 85.6

0.252 0.249 100.0 0.003 98.8

0.125 0.121 - −0.004 96.8

0.125 0.109 100.0 −0.016 87.2

Source: Reproduced with permission from the Royal Society of Chemistry [25]

formation rates of phosphate heteropolyacid being higher than that of the corresponding
silicate acid. The heteropolyacid was detected by its oxidation of a buffered solution of
thiamine to trichrome which was measured fluorometrically. The apparatus configuration
allowed two measurements at different times on each injected sample. The analytical
range was 30-600µg L−1 i n ratios 1:10 and 10:1 phosphate:silicate. Phosphate and
sulphide interfered with the determination of silicate when in similar concentrations to
the analyte. Hypochlorous acid and iodide were tolerated in 5:1 and 15:1 ratio to silicate.
Arsenite and sulphite were tolerated in 50:1 ratio to analyte. Sulphide and copper(II)
interfered with the determination of phosphate when present in similar concentrations to
the analyte. Iron(II) and iron(III) were tolerated in 1:1 ratio and hypochlorite and
carbonate in 25:1 ratio. Up to 60 samples per hour could be analysed.

14.4.1.4 Sulphate, silicate, cyanide, sulphide, chloride, nitrite, nitrate,
phosphate and alkalinity

Van Staden [30] reviewed flow injection analysis methods for the determination of
sulphate, sulphide, chloride, residual chlorine, nitrite, nitrate, phosphate, silicate, cyanide
and alkalinity in water and waste water. Sampling rate, concentration range, precision,
sample volume, chemistry, manifold technique and detection methods are summarised for
each procedure.

14.4.1.5 Arsenate, arsenite and phosphate

The influence of the chemical form of a given compound on its toxicity has a
representative example in arsenic; thus, As(III) is more toxic than As(V), the latter
exhibiting higher toxicity as arsenate than as monomethylarsonic acid (and this, in turn,
exhibiting higher toxicity than dimethylarsonic acid). This tradition of toxicity accounts
for the interest in the speciation of these compounds; there are some conventional
methods for speciation of arsenic in the literature (eg that based on its selective