Purification Methods
Two litres of a 5% aqueous solution of the phosphate are purified by adjusting the pH to 3.5 with glacial acetic acid (+ 3g of charcoal) and filtering. An equal volume of EtOH is added, the pH is adjusted to 8.0 (glass electrode) and the solution is stored at 3o overnight. The precipitate is filtered off, dissolved in 1.2L of distilled water, filtered and an equal volume of EtOH is added. After standing at 0o overnight, the crystals are collected at the centrifuge and washed with 95% EtOH, then absolute EtOH, ethanol/diethyl ether (1:1), and diethyl ether. [Sutherland & Wosilait, J Biol Chem 218 459 1956.] Its barium salt can be crystallised from water and EtOH. Heavy metal impurities are removed by passage of an aqueous solution (ca 1%) through an Amberlite IR-120 column (in the appropriate H+, Na+ or K+ forms). Di-K salt crystallises as a dihydrate from EtOH. [see McGready Biochemical Preparations 4 63 1955.] [Beilstein 17/8 V 247.]
