O-cresolphthalein complexone

Total calcium is most frequently measured by spectrophotometry using metaUochromic indicators or dyes. Of the metaUochromic indicators that change color on selectively binding calcium, o-cresolphthalein complexone (CPC) (3, 3"-bis [ [bis-(carboxymethyl)amino] -methyl] -5", 5"-dimethylphenolphthalein) (Figure 49-3) and arsenazo III are most widely used. These methods, although less accurate and reproducible than atomic absorption spectrophotometry, have been easier to automate on chemistry analyzers. 

Figure 4.7. (a) Two-line manifold for the spectrophotometric determination of calcium. Color reagent (o-cresolphthaleine complexone) and base are mixed and preheated in the first coil before the sample (30 xL) is injected and allowed to react in the second coil, the system being thermostated at 37°C. (b) Spectrophotometric determination of the total calcium content in serum at a sampling rate of approximately 110 samples/h. From left to right are shown a series of aqueous calcium standards containing (/) 25.0, (e) 20.0, (d) 15.0, (c) 10.0, (b) 5.0, and (a) 1.0 ppm, followed by three human serum samples, a serum pool (DSKK-K77), and the same serum pool sample with standard addition (25 p,L of a 500-ppm Ca standard plus 2.50 mL of serum pool). Each standard or sample was injected in quadruplicate. 

Postcolumn reagents PAR - 4-(2-pyridylazo)resordnol o-CPC - o-cresolphthalein complexone CAS - chrome azurol S PCV - pyrocatechol violet HQS - 8-hydroxyquinoline-5-sulfonic acid. 

Other Names Phenolphthalein, 3, 3"- [[ (carboxymethyl)amino]methyl]-5, 5"-dimethyl- 3,3 -5i5[A, A -fci5 (carboxyinethyl)aniinomethyl]-o-cresolphthalein 3,3 -5ii[Af,Af-di(carboxyinethyl)ainino-methyl]-o-cresolphthalein Cresolphthalein complexon Cresolphthalexon NSC 298195 Phthalein complexone o-Cresolphthalein complexon o-Cresolphthalein complexone o-Cresolphthalexon ... 

Colorimetric Methods. Colorimetric techniques using calcium-compiexing reagents such as o-cresolphthalein complexone and, more recently, arsenazo 111 and methylthymol blue have been... 

Arsenazo III (quantitation at 650-700 nm) at pH 5.6-7.8, initially introduced on the Kodak Ektachem dry reagent multilayer system, has now been adapted for use on a number of wet chemistry random access analyzers. Magnesium shows no interference but gross hemolysis may depress the calcium result. At low calcium concentrations, this technique gives slightly higher results than either the flame or o-cresolphthalein complexone (approximately 0.1 mmol/liter higher at a concentration of 1.60 mmol/liter). 

---