Methods and apparatuses for manufacturing a plurality of cartridges of medical buffering solution with a common ph

Abstract

The pH of a buffer or other medical solution in a plurality of containers can be adjusted and maintained by partially filling each container with a sodium bicarbonate solution so that a headspace remains over the solution. The headspace is filled with gas having a known CO 2 concentration, and a fixed and precise pH will result after the CO 2 is dissolved and the solution fully equilibrates.

1 . A method for adjusting the pH of a medical solution in a container, said method comprising:
 filling the container with a preselected volume of a bicarbonate solution to leave a predetermined volume of headspace over the buffer;   filling the headspace with a CO 2 -rich gas;   sealing the container to allow the CO 2 -rich gas to dissolve in the buffer to adjust a pH of the buffer to a desired value.   
     
     
         2 . A method as in  claim 1 , wherein the volume of bicarbonate buffer is in the range from 1.6 ml to 2.1 ml and the headspace volume is in the range from 0.16 ml to 0.21 ml. 
     
     
         3 . A method as in  claim 1 , wherein the CO 2 -rich gas has a CO 2  concentration of at least 75%. 
     
     
         4 . A method as in  claim 3 , wherein the CO 2  concentration is at least 98%. 
     
     
         5 . A method as in  claim 1 , wherein the contents of the container are maintained at ambient pressure after sealing. 
     
     
         6 . A method as in  claim 5 , wherein the cartridge has a moveable plug. 
     
     
         7 . A method as in  claim 1 , wherein the contents of the container are maintained at a pressure above ambient after sealing. 
     
     
         8 . A method as in  claim 7 , wherein the container has a moveable plug and the pressure is maintained by applying a spring-force to the plug. 
     
     
         9 . A method as in  claim 1 , further comprising holding the containers in a controlled atmosphere after filling, but before sealing so that the buffer pre-equilibrates with the atmosphere. 
     
     
         10 . A method as in  claim 9 , wherein the controlled atmosphere comprises the CO 2 -rich gas, wherein the headspace fills with the CO 2 -rich gas while the buffer pre-equilibrates.