Method for Determination of Lipin Phosphorus.

Abstract

Interest in the lecithin content of blood in syphilis necessitated an investigation of the various procedures for the estimation of phosphorus^1-8 or more specifically, lipin phosphorus.^2-6, 9 It was found that “test tube” oxidations by H₂SO 4 and HNO₃ had to be discarded. The danger of bumping with the small amount of reagents used became a source of great concern for micro-determinations.^2-5, 7 , 8 , 11 This led to the use of H₂SO₄ and H₂O₂ (suggestions of Baumann₁₁ and Briggs 3 ). Digestions were greatly facilitated, but certain difficulties were encountered. The figures obtained were not constant and often too high, the variations depending on the amount of H₂O₂ employed. 6

After much manipulation, a satisfactory technique was evolved, which may be detailed as follows:

Blood (0.5 cc.) is pipetted into 10.0 cc. of an alcohol-ether mixture (3:1) contained in a 50 cc. volumetric flask, preferably fitted with a glass stopper, and brought to boiling by inmersion in a water-bath. Digestion is continued for about 3 min. After cooling, alcohol-ether is added to the 50 cc. mark and the whole shaken vigorously. The filtrate (25 cc.) is transferred quantitatively to a casserol of 150 cc. capacity and evaporated to dryness over a water-bath. Then 10 cc. of HNO₃ (sp. gr. 1.42) is added and the dish rotated in such a way that the acid loosens the dried extract from the sides. 0.1 cc. H₂SO₄ (sp. gr. 1.84), 5 cc. KClO₃ (saturated solution) and 4 cc. of a mixture of saturated KNO₃, and a saturated solution of NaNO₃ (1:1) are introduced. The casserol is placed in the oven at 85-95° C. and digestion continued until the mixture becomes white. A safe interval is about 20 hours. A longer period does not matter. The white crystalline residue is dissolved in water by heating over a small free flame and transferred to a centrifuge tube (15 cc.), Including at least 2 washings, the total volume should not exceed 10 cc.