95] Preparation of ATP free of metal ions

Abstract

This chapter describes the preparation of ATP free of metal ions. The barium salt of ATP is dissolved in the tile presence of Dowex 50 resin, the resin is removed by filtration, residual barium ions are precipitated as barium sulfate, and the solution is neutralized to the desired pH with a base such as diethanolamine or tris(hydroxymethyl)aminomethane. The total amount of base added depends on the required pH but is usually between 3 and 4 equivalents per mole of ATP. It is found that if barium ATP is dissolved with acid instead of Dowex 50 resin, 4 equivalents of HCl are required per mole of ATP. The resin is added slowly to the suspension of barium ATP with thorough stirring. The ATP dissolves very slowly at first, but, after a certain amount of resin has been added, a point is reached where the characteristic white slurry of barium ATP suddenly disappears. This is usually accompanied by the conversion of the well-dispersed resin into a sticky mass. It is observed that if the solution contains less than the desired concentration of ATP, the cold solution of ATP is placed in a round-bottomed flask, and some water is removed from the cold solution in a rotary drier. The concentration of ATP is redetermined and adjusted to the desired value.