A laboratory technician left an open bottle of phosphate-buffered saline (pH 7.4, 0.01 mM phosphate) in a CO2 incubator overnight to allow it to warm up, returning the next day to find the pH has dropped to 6.0. What process has occurred?
Buffer is an aqueous solution of weak acid and its conjugate salt or weak base and its conjugate salt. It is used to resist the small amount of pH change under its buffer capacity. When this phosphate buffered saline left in CO2 environment for long time its aqueous part reacts with CO2 to form weak acid carbonic acid. Upto a certain time the buffered system can resist the pH change but for overnight with constant supply of CO2 the system forms H2CO3 on a regular basis so it changes the pH of the system slightly to the acidic range.
H2O + CO2 = H2CO3 (weak acid)
A laboratory technician left an open bottle of phosphate-buffered saline (pH 7.4, 0.01 mM phosphate) in...