Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 106

2.11 Bromate
2.11.1 Ion chromatography
The application of this technique is discussed under multianion analysis in section 12.2.4.
2.11.2 High performance liquid chromatography
Salov et al. [115] determined bromate (also chloride, iodide, bromide, chlorate and
iodate) in non saline waters by high performance liquid chromatography with an
inductively coupled argon plasma mass spectrometric detector.
The application of this technique is also discussed under multianion analysis in section
13.1.1.7.
2.12 Bromide
2.12.1 Titration methods
The National Water Council (UK) [116] had described a classical titration procedure for
the determination of bromide in river and seawaters in which bromide is oxidised to
bromate by sodium hypochlorite at about 100°C in a medium buffered to pH 6.2 with
phosphate. After reduction of the excess oxidant with formate, the bromate is determined
iodometrically. The method is applicable up to 140 mg L −1 bromide but is not designed
for trace amounts, for which an alternative method is available. Iodine and certain
oxidising or reducing agents interfere.
The potentiometric titration procedure described by Kuttel [117] for the determination
of chloride in non saline water has also been applied to the determination of bromide.
2.12.2 Spectrophotometric methods
Yonehara et al. [118] have described a method for the determination of traces of bromide
based on its catalysis of the pyrocatechol violet/ hydrogen peroxide reaction. The method
was rapid, simple and sensitive and did not involve an extraction step. Most ions
commonly occurring in non saline waters did not interfere except for iodide. Kinetic
studies showed that the effect of bromide on the oxidation reaction was enhanced in the
presence of large amounts of chloride (hydrochloric acid). Relative standard deviations
were 6.4 and 13% respectively for 0.034 and 0.01mg bromide per litre.
In a further method [119], the sample is treated with hydrochloric acid and with
chromotrope 2B (CI Acid Red) and 5 mmol L −1 potassium bromide. The time taken for
the colour to change from red to yellow as evaluated spectrophotometrically is measured
and compared with calibration data obtained to known bromide standards.
The indirect Spectrophotometric method of Fishman and Skougstad [120] and
Skougstad et al. [121] is based on the catalytic effect of bromide on the oxidation of