Influence of Nitric Acid and Hydrochloric Acid on the Calcium Determination by AAS in the Presence of Interference Inhibitor

Although natural water, such as river water and hot spring water can be analyzed for calcium directly by ICP-AES or ICP-MS after appropriate dilution, atomic absorption spectrophotometry (AAS) is still the major analytical method. Standard solutions or the water samples are generally acidified by hydrochloric acid for AAS, but the solutions are acidified by nitric acid for ICP-MS. Consequently, nitric acid is recently more common acid for acidification than hydrochloric acid. In the present work, calcium was determined by atomic absorption spectrophotometry in the presence of lanthanum or strontium as an interference inhibitor of silicon or aluminum. Nitric acid inhibited calcium absorption, which was evident in the presence of lanthanum or strontium. In contrast, hydrochloric acid showed only little inhibition with calcium absorption. Upon increasing the concentration of lanthanum over 2000 mg dm(-3), in contrast with strontium, decreased the interference of calcium absorption by nitric acid.