The suppressive interference of aluminum in the atomic absorption determination of calcium or magnesium has been commonly reported. Use of the high-temperature nitrous oxide-acetylene flame has also been shown to eliminate this interference. Prior to availability of this flame, use of controlling or releasing agents such as Sr salts, La, La+ EDTA, Ca, and oxine have been employed to compensate for this effect. Further tests in this laboratory using a Perkin–Elmer model 303 spectrophotometer and a fuel-rich air acetylene flame have shown 1% (w/v) of ammonium citrate or tartrate, oxalic acid, sodium nitrite, disodium EDTA, or sugar have little or no controlling action on aluminum at the pH of the dissolved salts. However, 0.5% (w/v) of hydroxylamine hydrochloride or 0.1% (w/v) of ethanolamine can compensate for 100-ppm A1 in determining 2-ppm Mg. Such releasing agents apparently exert a preferential reaction with either the aluminum or magnesium in the flame, allowing the magnesium compound to dissociate and manifest the atomic absorption phenomenon.
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