B DETERMINATION OF CALCIUM BY FLAME AAS

1 The sample is nebulised into an air-acetylene flame, where it is vaporised calcium compounds are atomised and the calcium atoms thus formed absorb radiation from a hollow-cathode lamp. The absorbance is measured at a wavelength of 422.7 nm. 

1 This procedure yieids a standard curve that is linear up to approximately 5 mg/L 

2 The detection iimit is approximately 2 mg/L in the digest. The determination limit is approximately 6 mg/L (7-25 mmol/kg in the dried plant material). 

3 If calcium contents for digestion 2.1 and 2.2 are higher than 1000 mmol/kg dry material, the solubility product of CaSO., can be surpassed in the digest a smaller sample has to be weighed out then. 

1 Since Ca atoms are easily captured in the flame into poorly dissociating compounds (like oxides), a releasing agent like lanthanum must be added. 

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