A METHOD FOR THE DETERMINATION OF LIPOID PHOSPHORUS IN BLOOD AND PLASMA

Abstract

When work was undertaken in this laboratory on the lipoid phosphorus of blood plasma it was hoped that the admirable method of phosphorus determination devised by Bell and Daisy,’ which had been found so useful for inorganic phosphates, could be utilized for this purpose. But the digestion procedure de- scribed by them under the subtitle “Total acid-soluble phos- phorus” failed in our hands to give satisfactory results with potassium acid phosphate solutions of known phosphorus con- tent. Since it appeared probable that the inaccuracies arose from the variable acidity of the digestion product, the writer resorted to the procedure of Randles and Knudson,2 which pro- vides somewhat more precise control of this factor. The results were then as a rule quite satisfactory. But occasional errors, usually negative, rarely positive, on known phosphate solutions, have shaken the writer’s confidence in this procedure and led him to devise a method not quite so simple but which is believed to be more reliable and which it is the purpose of the present paper to describe. The chief difficulty in carrying out the procedure of Randles and Knudson has been encountered in the control of the diges- tion process. If the heating is not vigorous enough to drive off all the nitric acid, full color development in subsequent stages is prevented. On the other hand, too vigorous heating may also produce errors, usually negative, rarely positive. The negative errors are attributable to local overheating, since the small volume of fluid present at the end of digestion is insufficient to