Chemistry Reference
In-Depth Information
Chapter 6
Anions in surface, ground, mineral, borehole
and pure waters
Limited numbers of determinations are available for each of these types of water.
However, in many cases, methods described for one type of water would be applicable to
other types. In all methods have been described for 18 different anions, including total
alkalinity, arsenite, borate, bromide, chloride, cyanide, fluoride, formate, iodide, nitrate,
nitrite, phosphate, selenate, selenite, sulphate, sulphide, sulphite, thiosulphate and uranyl
ion.
6.1
Surface waters
6.1.1
Total alkalinity
6.1.1.1
Titration method
Van Staden and Van Vleit [1] have described a simple automated titration procedure for
determining total alkalinity in surface waters. Up to 120 samples per h can be analysed
with a coefficient of variation of less than 1.4%.
6.1.2
Borate
6.1.2.1
Titration methods
Various workers [2,3] have described volumetric methods for the determination of borate
based on titration in the presence of a monohydric alcohol.
6.1.2.2
Spectrophotometric method
Cherkida and Flyantikova [4] have described a method for determining borate in surface
waters in which a 1 to 4 mixture of 2, 6 dimethyloctane 4, 6 diol and amyl alcohol is used
to extract boron from non saline waters. The boron is then re-extracted into aqueous
alkaline solution and can be determined colorimetrically, using fluorescein or H-resorcin
(2, 4-dioxybenzene-azo-8-hydroxy naphthalene-3-6 disulphoxy acid). The detection limit
is 0.05mg L
−1
.
The maximum light absorption of the aqueous solution of a triple complex of boron
with H-resorcin and with fluorescein is at 515nm and is characterised by a bathochromic
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