The Simplified Determination of Magnesium in Water by Calcium Carbonate Coprecipitation-Flame Atomic Absorption Spectrometry

Futoshi SUGIMOTO*, Teizo ISONO and Kazuhiko KOMURASAKI

Hyogo Prefectural Institute of Industrial Research, 1790-496 Nomura, Nishiwaki-shi 677-0054 Japan

The calcium carbonate coprecipitation method was studied for simplified determination of magnesium ions in water by flame atomic absorption spectrometry (F-AAS).
A 15 mL of 8 gCa L−1 calcium chloride and 15 mL of 20 w/v% potassium carbonate as a coprecipitant were added to sample water containing magnesium ions, followed by stirring for 30 min at room temperature. The resulting magnesium ions were quantitatively coprecipitated with calcium carbonate. The precipitate was collected onto a membrane filter (0.45 μm) and then dissolved with dipping for 15 min in 10 mL of (1+11) HCl. The solution was made up to 100 mL with distilled water to prepare the sample solution for F-AAS.
The detection limit for magnesium was 0.9 μg L−1(3 σ), and the lower limit of determination was 3.2 μg L−1(10 σ) in case of 200 mL of sample water.
This calcium carbonate coprecipitation method has no significant interferences in the analysis of water samples of 50 to 400 mL, and could be used as a preconcentration method for simplified determination by F-AAS of magnesium ions in water.

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