The pH of the stock solutions should not be adjusted prior to dilution; the pH is the negative log of the H* ion concentration so dilution by definition will result in a pH change. Always adjust the ph at the final buffer concentrations unless the procedure explicitly indicates that the diluted buffer is at an acceptable p nd ionic concentation, as in the case with some hybridization and electrophoresis buffers(Gallagher, 1999) Filtration n many applications a buffer salt solution is filtered prior to mixing with the other buffer components. An inappropriate filter can alter your solution if it binds with high affinity to one of the solution components. This is usually not as problematic with polar buffer salts as it can be with cofactors, vitamins, and the like. This effect is very clearly demonstrated when a solution is prepared with low levels of riboflavin. After filtering through a PTFE filter the filter becomes bright yellow and the riboflavin disappears from the solution Incomplete Procedural Information If you ask one hundred chemists to write down how to adjust the pH of a buffer, you'll probably receive one hundred answers, d only two that you can reproduce. It is simply tedious to describe in detail exactly how buffer solutions are prepared. When ading procedures, read them with an eye for detail: Are all details of the procedure spelled out, or are important aspects left out? The poor soul who tries to follow in the footsteps of those who have gone before too often finds the footsteps lead to a cliff Recognizing the cliff before one plunges headlong over it is a learned art. A few prototypical signposts that can alert you of an impending large first step follow Which salts were used to prepare the"pH 4 acetate buffer"? Sodium or potassium? What was the final concentration? Was pH adjustment done before or after the solution was brought to final volume? If the solution was filtered, what type of filter was used? What grade of water was used? What was the ph of the starting water source What Is the Storage Lifetime of a Buffer? a stable buffer has the desired ph and buffer capacity intended when it was made. The most common causes of buffer failure are The Preparation of Buffers and Other SolutionsThe pH of the stock solutions should not be adjusted prior to dilution; the pH is the negative log of the H+ ion concentration, so dilution by definition will result in a pH change. Always adjust the pH at the final buffer concentrations unless the procedure explicitly indicates that the diluted buffer is at an acceptable pH and ionic concentation, as in the case with some hybridization and electrophoresis buffers (Gallagher, 1999). Filtration In many applications a buffer salt solution is filtered prior to mixing with the other buffer components. An inappropriate filter can alter your solution if it binds with high affinity to one of the solution components. This is usually not as problematic with polar buffer salts as it can be with cofactors, vitamins, and the like. This effect is very clearly demonstrated when a solution is prepared with low levels of riboflavin. After filtering through a PTFE filter, the filter becomes bright yellow and the riboflavin disappears from the solution. Incomplete Procedural Information If you ask one hundred chemists to write down how to adjust the pH of a buffer, you’ll probably receive one hundred answers, and only two that you can reproduce. It is simply tedious to describe in detail exactly how buffer solutions are prepared.When reading procedures, read them with an eye for detail: Are all details of the procedure spelled out, or are important aspects left out? The poor soul who tries to follow in the footsteps of those who have gone before too often finds the footsteps lead to a cliff. Recognizing the cliff before one plunges headlong over it is a learned art. A few prototypical signposts that can alert you of an impending large first step follow: • Which salts were used to prepare the “pH 4 acetate buffer”? Sodium or potassium? What was the final concentration? • Was pH adjustment done before or after the solution was brought to final volume? • If the solution was filtered, what type of filter was used? • What grade of water was used? What was the pH of the starting water source? What Is the Storage Lifetime of a Buffer? A stable buffer has the desired pH and buffer capacity intended when it was made. The most common causes of buffer failure are The Preparation of Buffers and Other Solutions 37