Multianion analysis, miscellaneous methods - Determination of Anions in Natural and Treated Waters - page 723

2 −, 13.0 (uncertain). In addition, lead(II) ion forms moderately stable complexes with
such anions as 1M) and
A second objective of this work was to explore the potentialities of solvent
optimisation in flow injection analysis. In principle, the determination of such anions as
sulphate that form only moderately insoluble lead salts can be improved by judicious
addition of a cosolvent in order to lower the solubility. In fact, this has been done
frequently in classical gravimetric and volumetric determinations. It is necessary,
however, to address potential complications introduced by cosolvent addition, such as
inadequate electrode response or undesirable precipitation or complexation of analyte or
reagent ions with other substances that may be present in actual samples.
Flow injection analysis is rapidly developing into a powerful analytical tool with many
merits, such as broad scope, rapid sample throughput, and benefits accruing from
controlled dispersion. In such applications ion selective electrodes have been used in a
variety of ways, eg in direct sensing of analyte ion activities, in sensing the activities of
reagent ions after reaction with analytes, or in enzyme-catalysed reactions producing ions
that can be sensed with ion selective electrodes.
In the above work, Coetzee and Gardner [32] developed a simple flow injection
analysis system with lead(II) ion as reagent. They studied its applicability to the
determination of sulphate ion over a wide concentration range with high sample
throughput and made exploratory measurements with orthophosphate and triphosphate
ions as well.
14.4.2 Aqueous precipitation
14.4.2.1 Chloride, nitrate, bromide and phosphate
Flow injection analysis has been applied to the determination rain water of chloride,
nitrite, nitrate and phosphate [33,34].
14.5 Continuous flow analysis
14.5.1 Aqueous precipitation
14.5.1.1 Nitrate, chloride, sulphate and phosphate
A computer controlled multichannel continuous flow analysis system has been applied to
the measurement of nitrate, chloride and ammonium ions in small samples of rainwater
[34]. Continuous flow methods (flow injection analysis and continuous flow analysis)
have been used [33] to determine the principal constituents of rain water. While the two
methods are similar they differ in certain important respects, such as the rate of flow,
presence of air bubbles, diameter of the tubes and the reactions which are permissible
within the retention period limits set by the physical constraints. They were applied to
selected determinands (alkalinity, chloride, nitrite, nitrate, phosphate, sulphate,