The rate of calcium extraction during EDTA decalcification from thin bone slices as assessed with atomic absorption spectrophotometry.

The rate of calcium extraction with EDTA (ethylenediamine tetraacetic acid) from thin bone slices (300 micrometer-3 mm thick) was determined by aid of an atomic absorption spectrophotometer. A 0.5 mm thick bone slice was completely decalcified with 15% (0.40 M), 8% (0.22 M), and 4% (0.11 M) EDTA in 24 h, 3 days, and 5 days, respectively (vol. 15 ml, temp. 4 degrees C, pH 7.4). At 37 and 60 degrees C the speed of demineralization was slightly increased as compared with that at 20 degrees C, while no difference was observed between 4 and 20 degrees C. Bone slices with a thickness of 0.3, 0.5, 1 and 2 mm were decalcified -- in the same order -- in 24 h, 2, 3, and 5 days (8% EDTA, 4 degrees C, pH 7.4). At pH 7.4, the decalcification rate was a little slower than at pH 5.0 and 8.5. Agitation did not affect the decalcifying velocity, nor did the volume of the agent, except when the volume was very small. The demineralization of ordinary bone, containing both compact and spongy bone, was found to be more rapid than that of homogeneous bone reported earlier. The acidic buffers and New Decalc, which served as reference substances, exerted a more vigorous decalcifying effect thatn EDTA. K formate/formic acid buffer, pH 3.15, demineralized a 1 mm thick bone slice in 24 h and 2 days was needed with Na lactate/lactic acid buffer, pH 3.70. With New Decalc, pH 0.9, the corresponding demineralization was accomplished in 1.5 h. Atomic absorption spectrophotometer proved to be a useful tool in the evaluation of calcium extraction velocity from bone slices.