calcimetry

Calcimetry is the field of analytical chemistry that deals with measuring calcium content or calcium ion activity in a sample. It covers methods for quantifying calcium ions in solution, total calcium in solid materials, and calcium carbonate equivalence in substances such as limestone, cement, or soils. The term appears in geological, industrial, environmental, and clinical contexts, though many laboratories describe these procedures as calcium analysis or calcium determination.

Prominent calcimetric techniques include complexometric titration with ethylenediaminetetraacetic acid (EDTA), performed in buffered solution around pH 10 with indicators such as Eriochrome Black T or Calmagite. Magnesium can be masked to measure calcium specifically, or separate titrations can quantify both ions. Gravimetric methods determine calcium by precipitating it as calcium oxalate or calcium tungstate and weighing the solid. Instrumental methods include atomic absorption spectroscopy (AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES) or mass spectrometry (ICP-MS) for direct calcium content. In clinical chemistry, colorimetric assays using calcium-specific reactions (for example o-cresolphthalein complexone or arsenazo III) provide measurable color changes proportional to calcium concentration.

Applications of calcimetry include assessing water hardness, evaluating lime and cement raw materials, measuring soil calcium carbonate content, and determining calcium in foods or biological samples. Interferences from other ions, matrix effects, and calcium-binding species can affect accuracy, requiring appropriate sample preparation and method selection. The term calcimetry is less common than calcium analysis but is used in some specialties to denote calcium quantification methods.