The importance of pH and buffers

A key parameter in any water based solution is called the pH.  Water is a molecule made up of three atoms, two from hydrogen and one from oxygen: H2O.  However, this is the idealized view.  Depending on the conditions, one of the hydrogen atoms can disassociate from the water molecule, leaving a bare hydrogen carrying a positive charge, H+, and the second hydrogen atom bound to the single oxygen atom carrying a negative charge, OH.

The concentration of hydrogen ions in pure water at room temperature is 10-7.  By convention, this is called the pH and written as pH=7.  If the pH is less than 7, the solution is called acidic.  If the pH is greater than 7, the solution is called basic.

Pure water is easily contaminated, which can shift its pH value.  Rain water is pure in the clouds.  It forms from condensation of water vapor. In the clouds, it would have a pH=7.  However, by the time it reaches the ground, some atmospheric gases have dissolved into the water drop.  These gases, primarily carbon dioxide, lead to, say, a ten times higher concentration of hydrogen ions, or 10-6.  Thus, the rain reaching the ground is acidic, with a pH of 6.  A similar effect could occur if a glass of water is exposed to air, gases will dissolve into the water changing its pH.

One can add small amounts of certain chemicals to the water to prevent wild swings in pH.  This solution is called a buffer.  A buffer resists changing pH when hydrogen ions are added or subtracted to the solution.  The buffer resists changes because the chemicals added to the water take the hydrogen ions and incorporate them into molecules, removing the bare ion from the solution.

Many biological molecules will only function properly in a narrow range of pH values.  Blood, for instance, is a natural buffer.  The normal pH range for human blood is from 7.35 to 7.45.  If your blood’s pH falls below that range, you have acidosis.  Symptoms of acidosis include fatigue, confusion, and sleepiness.  Acidosis is one symptom of untreated diabetes.

In early 1922, Collip did not realize that the solubility of insulin depended critically on the pH value of the solution in which it was dissolved.  When trying to scale up production of insulin during the spring of 1922, he was apparently reproducing all the steps he took previously, but using larger containers.  Unbuffered water will change its pH based on apparently insignificant factors, like the shape of container it is held in and how long it is exposed to air.  These insignificant factors led to the crisis, the inability to produce usable insulin.