Method for preparing aqueous solutions of a defined pH

A method for preparing an aqueous solution of a defined pH comprising an acid, a base and one or more additives, wherein the method comprises the steps of:

• a) calculating theoretical concentrations of acid, base and additive for each of a plurality of solutions having a theoretical pH corresponding to the defined pH, and each of the plurality of solutions having a different additive concentration within a range of different additive concentrations, wherein said calculating is carried out using the Henderson-Hasselbach equation in combination with the Debye Huckel theory;
• b) for each solution, calculating a value for ΔpH, being the difference between the theoretical pH and a value for actual pH, for each of the plurality of solutions having a different additive concentration;
• c) generating a mathematical model describing a relationship of ΔpH with additive concentration;
• d) selecting the defined pH and additive concentration for the aqueous solution to be prepared;
• e) using the mathematical model generated in step c) to calculate ΔpH for the defined pH and additive concentration;
• f) calculating a ΔpH-corrected pH by summing the defined pH and ΔpH;
• g) using the ΔpH-corrected pH to calculate concentrations of acid and base for the preparation of the aqueous solution including the additive by using the Henderson-Hasselbach equation in combination with the Debye Huckel theory;
• and
• h) preparing the aqueous solution including the one or more additives using the concentrations of acid and base calculated in step g).

A method for preparing an aqueous solution of a defined pH, comprising an acid, a base and an additive, wherein the method comprises the steps of:

• a) calculating a theoretical pH for the aqueous solution using the Henderson-Hasselbach equation in combination with the Debye Huckel theory;
• b) calculating a ΔpH-corrected pH for the aqueous solution by comparing the theoretical pH with a pH value calculated from an equation determined from a mathematical model of the difference between the theoretical pH and a value for actual pH of each of a plurality of solutions having a different additive concentration within a range of different additive concentrations;
• c) using the ΔpH-corrected pH to calculate concentrations of acid and base for the preparation of the aqueous solution including the additive using the Henderson-Hasselbach equation in combination with the Debye Huckel theory;
• and
• d) preparing the aqueous solution including the additive using the concentrations of acid and base calculated in step c).

An apparatus for preparing an aqueous solution of a defined pH, wherein the apparatus comprises a metering device capable of feeding into a mixing device an acid, a base, and one or more additives, wherein the metering device operates under control of control apparatus for

• a) calculating theoretical concentrations of acid and base for each of a plurality of solutions having a theoretical pH corresponding to the defined pH, and each of the plurality of solutions having a different additive concentration within a range of different additive concentrations, wherein said calculating is carried out using the Henderson-Hasselbach equation in combination with the Debye Huckel theory;
• b) for each solution, calculating a value for delta pH, ΔpH, being the difference between the theoretical pH and the actual pH;
• c) generating a mathematical model describing a relationship of ΔpH with additive concentration;
• d) selecting the defined pH and additive concentration for the aqueous solution to be prepared;
• e) using the mathematical model generated in step d) to calculate ΔpH for the selected defined pH and additive concentration;
• f) calculating a ΔpH-corrected pH by summing the defined pH and ΔpH;
• g) using the ΔpH-corrected pH to calculate concentrations of acid and base for the preparation of the aqueous solution including the one or more additives by using the Henderson-Hasselbach equation in combination with the Debye Huckel theory.

An apparatus for preparing an aqueous solution of a defined pH, wherein the apparatus comprises a metering device capable of feeding into a mixing device an acid, a base, and one or more additives, wherein the metering device operates under control of control apparatus for

• a) calculating theoretical concentrations of acid, base and additive for each of a plurality of solutions having a theoretical pH corresponding to the defined pH, and each of the plurality of solutions having a different additive concentration within a range of different additive concentrations, wherein said calculating is carried out using the Henderson-Hasselbach equation in combination with the Debye Huckel theory;
• b) for each solution, calculating a value for ΔpH, being the difference between the theoretical pH and a value for actual pH, for each of the plurality of solutions having a different additive concentration;
• c) generating a mathematical model describing a relationship of ΔpH with additive concentration;
• d) selecting the defined pH and additive concentration for the aqueous solution to be prepared;
• e) using the mathematical model generated in step c) to calculate ΔpH for the defined pH and additive concentration;
• f) calculating a ΔpH-corrected pH by summing the defined pH and ΔpH;
• g) using the ΔpH-corrected pH to calculate concentrations of acid and base for the preparation of the aqueous solution including the one or more additives by using the Henderson-Hasselbach equation in combination with the Debye Huckel theory.