Method F-020G The Simple Flame Photometric Determination of Calcium
If aqueous samples of calcium are to be analysed which contain no interferent ions the following method should be employed.
Method:
From the Sherwood 1000 ppm calcium stock standard prepare diluted standards of 100, 75, 50 and 25 ppm using deionised water as diluent.
If the samples to be analysed are of lower concentration then prepare 50, 40, 20 and 10 ppm standards. A top standard of less than 50 ppm is not entirely suitable
due to low temperature flame photometry being insensitive to calcium at low concentrations.
Aspirate the standards into the flame photometer and record the stable readings.
Plot a graph of intensity vs concentration on linear graph paper.
Aspirate the aqueous sample.
From the calibration graph obtain the sample concentration.
If there are interferent ions present, calcium should be precipitated as calcium oxalate, dissolved in HCIO4 and then analysed.
