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Advisor(s)
Abstract(s)
A sequential injection methodology for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples is proposed. A single manifold is used for the determination of the three analytes, and the same protocol sequence allows the sequential determination of calcium and magnesium (the sum corresponds to the water hardness).
The determination of both metals is based on their reaction with cresolphtalein complexone; mutual interference is
minimized by using 8-hydroxyquinoline for the determination of calcium and ethylene glycol-bis(0-aminoethyl ether)-
N,N,N',N'-tetraacetic acid (EGTA) for the determination of magnesium. Alkalinity determination is based on a reaction
with acetic acid, and corresponding color change of Bromcresol Green. Working ranges of 0.5 - 5 mg dm” for Ca, 0.5 -
10 mg dm” for Mg, and 10 - 100 mg HCO3’ dm’3, for alkalinity have been achieved. The results for water samples were
comparable to those of the reference methods and to a certified reference water sample. RSDs lower than 5% were obtained, a low reagent consumption and a reduced volume of effluent have been accomplished. The determination rate for calcium and magnesium is 80 h’1, corresponding to 40 h’1 per element, while 65 determinations of alkalinity per hour could be carried out.
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Pedagogical Context
Citation
"Analytical Sciences" . ISSN 0910-6340. 20: 8 (2004) 1205-1210
Publisher
The Japan Society for Analytical Chemistry