Oleh: Juli Astuti, Herawati (Akademi Kimia Analisis Bogor)
The preliminary study on Lanthanum addition in calcium determination using Atomic Absorption Spectrophotometer (AAS) has been done. This study is aimed to find out the proper concentration of Lanthanum which can solve the problem of phosphate interference in calcium determination. In calcium determination, the absorbance of 4 mg/L calcium standard was 45 % reduced because of the interference of the presence of 20 mg/L phosphate. The result of this preliminary study is that the addition of 15 mg/L (minimum) Lanthanum to the sample which consist of 3 mg/L calcium and 3 mg/L phosphate can increase the absorbance by 41 %. This result indicates that Lanthanum can solve the problem of phosphate interference in determining calcium.