Sugar in 0.02 cc. Blood by the Method of Folin and Malmros.

Abstract

The method of Folin and Malmros permits of drawing a second sample of the protein-free blood centrifugate in order to duplicate the determination. In the training of assistants, I have taken advantage of this in order to check their technique but in no case was an absolute check obtained. On trying it myself I did not get an absolute check. The reason for this discrepancy may be that sufficient time was not allowed for a diffusion-equilibrium of the sugar between the precipitate and the centrifugate with consequent continuation of the diffusion during the centrifuging and difference in the concentration of the upper and lower part of the centrifuge tube. Another possible cause for the variation is the destruction of sugar in the centrifugate with time, as some of these checks were made 6 or more hours later. Another source of error is in the time taken for making the readings. The 2 solutions of prussian blue, I of the blood centrifugate and the other of the standard sugar solution, change on standing and the rate of change is not the same in the 2 solutions. Therefore, one must work rapidly in making the readings. Since the above method of check does not check the technique of measuring the blood sample and since 2 samples of 0.1 cc. of blood can not be taken out of the same drop from the cut finger and since successive drops may vary in sugar content, we have reduced the quantity to one-fifth. Our technique is as follows: using B. & L. apparatus, including the blood pipette made for the hemoglobin determination: Measure 0.02 cc. of blood and blow it into 2 cc. of tungstic acid solution contained in a 5 cc. test-tube.