pH Buffer Solution Capsules

[RCCOLA]

I see quite a few threads about buffer solution on here. Just thought I'd share what works well for me. I initially bought big containers of pre-mixed buffer solution not knowing that it expired after a few months.

What happens is the pH 7.0 solution grows mold. You can tell b/c its color turns darker. I checked mine one day and it had a disgusting mold blob growing on top of it. My pH 4.0 never has done this (I believe b/c of the low pH)

Anyways, I started buying powder pH buffer capsules and mix them with distilled water to make my solutions. I always have them on hand and they don't expire, It's a great value for the amt of solution you can mix total.

Here's what I use:

http://www.amazon.com/dp/B004CB5C74/?tag=skimlinks_replacement-20

 

[mabrungard]

+1 on using these buffer capsules to create your own calibration solutions with distilled water. Those are what I use. I think each capsule is combined with 100 ml of distilled water. That amount of buffer will last for at least 6 months if you keep it tightly capped. This is way cheaper than buying premixed buffer solutions. You do need to have an accurate way of measuring out your water. Weighing 100 grams of water with a precision scale is probably the best way.

 

[ajdelange]

That amount of buffer will last for at least 6 months if you keep it tightly capped. This is way cheaper....

Didn't know you were a Scottie. That is, er, verrrrry economical for sure! The ones I use (Hach) are $0.42 each so it costs me less than a dollar each time I make new buffers which I do if the old ones are more than a week or so old and certainly every time I brew or if I've done a lot of cals. New buffer is cheap and always a good idea.

You do need to have an accurate way of measuring out your water. Weighing 100 grams of water with a precision scale is probably the best way.

Or you could use a mixing cylinder, even class B but neither is necessary by any means. These are buffers which means they are intended to resist change in pH from any acidic or basic stress. As DI water has tiny buffering capacity it doesn't represent much of a stress. If I make up a 50 millimolar pH 7 phosphate buffer (that's what the Hach pH 7 buffer is assuming the salts are sodium salts) and screw up and add the powder which is intended for 50 ml (about 335 mg) to 100 mL of DI water by mistake the pH calculates out to 7.008 (as opposed to 7.000 for the exactly correct amount of water). The tolerance on these buffers is ±0.02 so by using twice as much water as I should I change the tolerance to ±0.022. If you are off 10% or so on the water amount I don't think that is anything to worry about. Many companies sell little plastic containers designed to contain buffers and these are often marked to 50 and 100 mL. Those markings should be plenty good enough.