Anions in potable waters - Determination of Anions in Natural and Treated Waters - page 512

Table 7.17 Comparison of analyses of drinking waters for NO 3 − concentration by GC-
ECD and ISE. Numerical designations refer to selected municipal water
supplies in Crowley County, Colo., USA. Unless otherwise specified
concentrations are expressed in ppm (w/w)

Concentration NO 3 − (mg L −1 )

Site

GC-ECD a ISE b

Boulder, Colo. 0.40 -

TW0011 44 48

TW0012 42 46

TW0013 51 52

TW0014 16 16

TW0015 35 36

TW0016 12 13

a Electron capture gas chromatography
b Ion selective electrode measurement
Source: Reproduced with permission from Elsevier Science [73]

difference, generally a nitrate concentration which is 5% of the nitrite concentration can
be detected). In Table 7.17 the results are shown of a comparative study of the electron
capture gas chromatographic microtechnique vs ion selective electrode measurements.
The close agreement (usually within 5%) of the totally independent methods used for the
analysis of identical samples is an excellent demonstration of the efficacy of the methods.

7.21 Perchlorate

7.21.1 Polarography

The application of this technique is discussed under multianion analysis in section
14.10.2.1.

7.22 Phosphate

7.22.1 Spectrophotometric method
Matsubara et al. [75] determined trace amounts of phosphate (and arsenate) in potable
water by Spectrophotometric detection at 627nm of their heteropoly-malachite green
aggregates following preconcentration by nitrocellulose membrane filtration.