Abstract
Many investigators have assumed that the calcium of heparin is not available for oxalate precipitation, as performed in the Clark-Collip 1 modification of the Kramer-Tisdall 2 method. Interest in this question was aroused by the difference of opinion of various workers regarding the concentration of calcium in serum and in heparin plasma. Cantarow, 3 in a series of 100 determinations, using heparin as an anticoagulant, found that the calcium level was 0.5 mg. to 1.0 mg. less in each 100 cc. of plasma than in the corresponding serum. Greisheimer and Arnold, 4 and Loucks and Scott 5 have published data on this question.
In the present study several different samples of heparin were used. Heparin was added to redistilled water, to calcium chloride solutions, to plasma, and to serum. These heparinized solutions, with corresponding non-heparinized solutions as controls, were analyzed for calcium by the Clark-Collip modification of the Kramer-Tisdall method.
Dogs' blood served as the source of plasma and serum. All reagents were tested and found to be calcium-free. A microburet whose outlet was ground and fitted with a hypodermic needle was used for titration.
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