The reaction between calcium and alizarin (ALZ) was investigated for the spectrophotometric determination of trace amounts of calcium. The cationic surfactant, cetyltrimethylammonium bromide (CTAB) was useful to increase the sensitivity. The beta-correction method was applied for the determination of the properties of the Ca-ALZ complex instead of ordinary spectrophotometry. Results showed that the complex formed, expressed as Ca(ALZ)2, has a real molar absorptivity equal to 3.74×10³ L mol-1 cm-1 at 630 nm.
beta-correction principle; calcium complex; alizarin; trace calcium
