title: Some observations on the nature of the calcium-cresolphthalein complexone reaction and its relevance to the clinical laboratory.
abstract: The reasons for the non-linearity of the standard curve for the calcium-cresolphthalein complexone reaction have been investigated. Calcium forms both 1:1 and 2:1 complexes with cresolphthalein complexone; at low calcium concentrations the 1:1 complex predominates and causes non-linearity. At high calcium concentrations the cresolphthalein complexone concentration becomes limiting, resulting in flattening of the calibration curve. It is recommended that two-point calibration of the assay be performed using a low calcium standard rather than setting on the baseline.
authors: Department of Chemical Pathology, Middlesex Hospital Medical School, London, UK.
authors: C M
authors: CM
authors: Corns
authors: C J
authors: CJ
authors: Ludman
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002138:Calibration; D002614:Chelating Agents; D007700:Kinetics; D010635:Phenolphthaleins; D013054:Spectrophotometry, Atomic
chemical_list: D002614:Chelating Agents; D010635:Phenolphthaleins; C017845:2-cresolphthalexon; D002118:Calcium