Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 171

equilibrium potential in the bulk of the solution. Under the conditions outlined in this
modified method a stable electrode potential can be obtained in a short time in stirred
solutions as dilute as 20µg L −1 fluoride.
Fucsko et al. [335] have described a flow injection ion selective electrode
determination of fluoride in non saline waters. This has a sampling rate of 40 samples/h
at concentrations <10 −6 M and a rate of 60 samples/h at concentrations >10 −5 M.
2.31.7 Ion chromatography
The application of this technique is discussed under multianion analysis in section 12.2.1.
2.31.8 High performance liquid chromatography
The application of this technique is discussed under multianion analysis in section
13.1.1.5.
2.31.9 Ion exchange chromatography
Okabayashi et al. [336] collected fluoride ion selectively on an anion exchange resin
loaded with alizarin fluorine blue sulphonate.
2.31.10 Gas chromatography—atmospheric pressure helium microwave
induced plasma emission spectrophotometry
This technique has been applied to the determination of picogram quantities of fluoride in
water [337]. The emission line of fluorine at 685.6nm was used for detection.
Miyazaki and Bransho [324] determined fluoride indirectly in non saline waters with
lanthanum alizarin complexone and inductively coupled plasma emission spectrometry.
The ternary lanthanum-alizarin complexone-fluoride (La-AC-F) complex was extracted
into hexanol containing N,N-diethylaniline, and the extract analysed directly by ICPES
for the determination of fluoride. Measurement of the lanthanum(II) 333.75nm emission
line and comparison with a calibration graph enabled fluoride concentrations as low as
0.59µg L −1 to be determined in river water (polluted and unpolluted), coastal seawater
and potable water.
2.31.11 Miscellaneous
Perez Ruiz [338] describes a catalytic-kinetic method for determining nanogram amounts
of fluoride in non saline waters based on its inhibiting effect on the catalyst in the iron
(III)-catalysed photooxidation of thionine. The rate measurements are made by
monitoring the decreasing absorbance after illumination for a fixed time. Relative
standard deviation was 2.58% for a concentration of 152mg of fluoride mL −1 ( n =10).