THE MICRO DETERMINATION OF CALCIUM IN WHOLE BLOOD, PLASMA, AND SERUM BY DIRECT PRECIPITATION
1921; Elsevier BV; Volume: 49; Issue: 2 Linguagem: Inglês
10.1016/s0021-9258(18)85984-1
ISSN1083-351X
Autores Tópico(s)Analytical Methods in Pharmaceuticals
ResumoMethods for the determination of calcium, if classified according to the manner of obtaining solutions from which the calcium may .beprecipitated, fall into three groups: (1) Destruction of the organic matter (proteins) by ashing or by digestion with an oxidizing mixture and solution of the ash in hydrochloric acid (l-8).(2) Precipitation of the proteins, as by picric, tungstic, or trichloroacetic acids, and use of aliquot part of the filtrate (9, 10).(3) Direct precipitation, in the presence of proteins, so far only applied to whole blood, plasma, and serum (11)(12)(13)(14)(15).Although every method utilizes the oxalate ion for the precipitation of calcium, considerable variation is observed in the manner of obtaining the H ion concentration at which pure calcium oxalate is most completely precipitated.After obtaining the washed calcium oxalate the following procedures have been used for the actual estimation of the calcium:1. Gravimetrically, by conversion to CaO or CaS04 and weighing (1, 2, 11).2. Volumetrically; (a) by titration with potassium permanganate (3, 6-8, 10, 12-15) and, (b) by solution in excess acid and titration of excess acid (5).3. Nephelometrically, by conversion into a calcium soap (9). 4. Calorimetrically, by decolorization of ferric thiocyanate with oxalates (4).5. Iodometrically, by solution of CaO in excess HCl, the excess acid then determined by estimating t'he amount of iodine liberated (5). 5 I-+ 103-+ 6 H+ -+ 3 Hz0 + I,.
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