When measuring calcium by atomic absorption spectrophotometry, which is essential?

When measuring calcium by atomic absorption spectrophotometry, the inclusion of lanthanum oxide is crucial as it helps to mitigate the effects of phosphates that may interfere with the accurate measurement of calcium concentrations. Phosphates can form complexes with calcium, thus potentially leading to an underestimation of calcium levels in the sample. By using lanthanum oxide, which chelates phosphates, it prevents the interference from these competing ions, allowing for a more accurate determination of the calcium concentration in the sample.

Using appropriate reagents and additives in atomic absorption spectrophotometry is vital for achieving reliable results, and the role of lanthanum oxide highlights the importance of managing interference in analytical chemistry.