Purification of Phosphatides

After administration of labeled phosphate, free phosphate and also some of the acid-soluble fractions of organs are often much more active than the phosphatide fraction. It is therefore of great importance to purify the phosphatides and free them from all other active fractions. Levene s classical method, which is based on the extraction of the mineral constituents by shaking an ether solution of phosphatides with a water solution of acetic acid, does not remove the labeled free phosphate. When, however, acetic acid is replaced by hydrochloric acid, an effective separation can be obtained (69). The effectiveness of this method of purification is seen from the figures of Table XII (9). 

Number of purifications Activity of ether solution Activity of water solution 

Shaking the ether solution of the phosphatides with ten drops of saturated disodium phosphate solution containing excess solid disodium phosphate was found also to be very effective in removing traces of radioactive phosphorus (62). 

Taurog and his associates (174) found that phosphatides are absorbed quantitatively from a petroleum ether solution by magnesium oxide 0.6 g. magnesium oxide suffices to absorb 0.85 mg. of phosphatide phosphorus dissolved in 15 ml. petroleum ether. Use of 1.75 g. magne.sium oxide is however preferable when choline-eontaining phosphatides have to be separated from non-choline-containing phosphatideS. The separation is based on the elution of the choline-containing phosphatides by methyl alcohol. 

The separation of choline-containing phosphatides from non-choline-containing phosphatides can however also be accomplished by first dissolving the phosphatides in methanol and then treating this methanol solution with magnesium oxide. The following procedure is used. 

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