The classic Clark-Collip method for calcium is based on which assumption?

The Clark-Collip method for determining calcium levels in serum relies on the assumption that calcium will be precipitated as an oxalate. In this technique, calcium ions in the solution are reacted with oxalic acid to form calcium oxalate, which is an insoluble precipitate. By creating this precipitate, the method enables the separation of calcium from the liquid portion of the serum, allowing for its quantification.

This precipitation step is crucial because it ensures that the calcium can be measured accurately without interference from other substances present in the serum. The concentration of the formed precipitate is then related back to the amount of calcium originally present in the sample. It is this fundamental principle that allows for an effective and reliable assessment of calcium levels in biological samples using the Clark-Collip method.