The Influence of Phosphate on the Determination of Calcium by Flame Methods of Analysis—A New Approach

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Abstract
The depression of the analytical signal of calcium by phosphate ion when using turbulent (H2/02 and H2/A/entrained air) and laminar (C2/H2/air) flames in flame spectro-ietry is studied. Measurements of flame emission of calcium as a function of calcium to phosphate and pyrophosphate molar ratios for various flame heights in both turbulent and laminar flames are made. The phosphate interference when using turbulent flames is shown to be a result of a slow vaporization of the calcium phosphate particles. The phosphate interference when using laminar flames with chamber type aspirators is only important at high calcium and phosphate concentrations. The cause of the interference is probably a result of either slow vaporization of the calcium phosphate particles or a slow rate of change of the orthophosphate to pyrophosphate during the decomposition step.