Do pH buffers used in lab experiments go "bad," or become less/more acidic over time?

Question

This is for the "source of error" part of a lab report. THankyou very very much!

Answer 1

The pH buffers used in a lab experiment can go "bad" at different rates depending on the way they're stored. If your buffer is always stored in a closed container, then the contamination is usually pretty low and the buffer can last for a long time. However if your buffer is constantly exposed to open air and moisture, the pH of your solution can vary quite a bit. I'm not sure if you are familiar with the effect of boiling "tap" water, but boiling the water gets rid of carbonic acid in the solution, similar to the acidity found in a soft drink. So over time, if a buffer is exposed to air, the buffer will tend to become more acidic if no other factors (contamination by other careless people in the lab for example :P) are present. Hope this helps!

Answer 2

They go "bad". As you calibrate your probe, you are slowly introducing more water, air diffusion will change the pH.

But, this usually not a source of error as the "lifetime" of the buffers could be between 1 to 5 years. Just need to take care to replace them in time.

Answer 3

Apart from the aforementioned reasons, some buffers are a fair growth medium for certain microorganisms. Thus after some time you have micro-organisms growing in the buffer and of course changing its concentration and consistency since they are feeding from it and excreting byproducts in it.
That's why commercially available buffers for calibrating pH-meters usually have antimicrobial additives.

Answer 4

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