A couple of ph meter questions?

Is the buffer solution reusable? It's in a big packet for a one time use. Also it say's it's pre-calibrated, but then says to check before each use. It only came with the 7.01 buffer, should I check with that, or just use as is until I can get the 4.01 buffer as well?

And lastly can you use the buffer solution to store the tip in, conflicting reports on this.

Well, I'd want to check the calibration with each use until I got familiar with the units tendency to drift.

And no, you really need to get a storage solution. Even pH neutral water can strip ions from the probe over time.

The purchase of the meter is only the beginning. You need 7 and 4 buffers for calibration (for beer) and the storage solution. I also use the cleaning solution before storing. Never tried to reuse the calibration solutions, I have a hard enough time trusting the new solution!

I get them from eseasongear

wildwest450 said:

Is the buffer solution reusable? It's in a big packet for a one time use. Also it say's it's pre-calibrated, but then says to check before each use. It only came with the 7.01 buffer, should I check with that, or just use as is until I can get the 4.01 buffer as well?

And lastly can you use the buffer solution to store the tip in, conflicting reports on this.

Click to expand...

I use only enough solution to submerge the probe when calibrating. Do not re-use as it may be contaminated.

It's best to calibrate each time. Using only 7 buffer to calibrate is ok. AFAIK, it's better to use 7 and the buffer nearest the anticipated ph reading (in our case that would be 4).


You'll want to purchase the storage solution. If not stored properly, the bulb will have to be replaced more frequently

But, do keep the chart on the bag of solution you have. pH is temp dependant and that pouch is a good reference.

Thanks, it's nice to know I only have 1/10 of the stuff needed to check ph. Living in a socially repressed state I guess i'll have to order more crap.

wildwest450 said:

Thanks, it's nice to know I only have 1/10 of the stuff needed to check ph. Living in a socially repressed state I guess i'll have to order more crap.

Click to expand...

Ha. It's not that bad. 4 buffer, 7 buffer, and storage solution is the bare minimum. And you don't need much for storage or calibration.

I use distilled water to rinse the probe and the storage buffer fills the cap before I put the meter away.

It is essential to calibrate with 2 buffers which bracket the pH range you wish to measure. For brewing 4 and 7 are fine. A pH electrode is characterized by offset, slope (and iso electric pH) and it takes 2 buffers to get values for both of those (error is insensitive to iso electric pH and so that's usually just assumed to be 7). With only one buffer you can estimate either slope or offset but you must guess at the other to do so.

It is best to use freshly prepared buffers. A moment's inattention - didn't rinse the probe with DI water between buffers or after measuring beer/wort... or didn't blot the probe dry and you have dilution and/or contamination. The best bet here are the little capsules that contain enough powder for 50 mL or 100 mL of buffer. Add the contents of the capsule to the proper volume of DI water and presto, fresh buffer. Next best, or just as good technically but more expensive) are the little individual pouches.

I tried to do a recal just the other day using buffers that were a week old and I only got 93% slope. As the buffers are stable longer than that I'm sure the problem was contamination on my part.

If your meter tells you slope and offset at each calibration make a note of those. By looking at how these change over time you can see how fast your electrode is aging.

Do use the manufacturers recommended storage solution. Sometimes they say 7 buffer but most of the time it is potassium chloride. Using what they recommend keeps the surface of the bulb properly hydrated with the right ions "dissolved" in the glass. DI water will leach these out and it will be necessary to recondition the electrode to recover. Reconditioning will also be necessary if the glass dries out.

You shouldn't need the pH vs temperature data on the buffer package if your meter is equipped with ATC. The numbers on the packets are standard numbers published by NIST and the microprocessor in you meter has those in its memory. If you are going to calculate pH from mV readings and temperature then you do need those numbers but I doubt you will be doing that.

Although ATC means you don't have to do it this way it is best to have the buffers and the test solution all at the same temperature. If the isoelectric pH is much different from 7 this will give more accurate readings.

Check aquarium stores for the calibration solution. Last time I bought packets they were something like 5 packs for $4.

B

$1.09 http://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=4512

For comparison, you can get a box of 50 of the pillows (which are used to make up fresh 50 mL of buffer), for $15.55 or 15 of them for $8.35. Here's the URL. It's so long you might just want to go to www.hach.com and type in product number 22270-66.

http://www.hach.com/hc/search.produ...TVRVNU9EZ21aM1ZsYzNSWlQwdEVRZz09QlRFeU9EVQ==|

bad coffee said:

$1.09 http://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=4512

Click to expand...

Thanks! That's by far the cheapest option for pre made solution, i just placed an order.

ajdelange said:

For comparison, you can get a box of 50 of the pillows (which are used to make up fresh 50 mL of buffer), for $15.55 or 15 of them for $8.35. Here's the URL. It's so long you might just want to go to www.hach.com and type in product number 22270-66.

http://www.hach.com/hc/search.produ...TVRVNU9EZ21aM1ZsYzNSWlQwdEVRZz09QlRFeU9EVQ==|

Click to expand...

Sorry to resurrect an old thread, but it seemed more appropriate than starting a new one. What do you use to mix these pillows in? I would assume you want to make sure you're exactly at 50 ml of distilled water, otherwise you'll have a less precise buffer concentration for calibration. Hach has 50 ml glass beakers on their site. I like how much cheaper of an option the powders are to the pre-mixed packets (which run about $1.50/pack = $3/calibration) but my only reservation is not being able to measure precisely 50 ml of water. The glass beaker description states, "Volumes and graduations are approximate.."

Thoughts?

Got a scale that measures grams? 1ml water is 1g (at 4*C)

For the most precise work you would buy a Class A mixing cylinder, dump in the powder and add water to make exactly 50 mL at the temperature for which the cylinder is made. This level of accuracy is not necessary as the dilution sensitivity is small and if you get 49 or 51 mL the error is going to be less than the uncertainty in the buffer. For example, if we make a 1.5 mmol/L 7.0000 phosphate buffer and err by 2% in the amount of water used the pH shifts to 6.9915 (theoretically).

I use an inexpensive plastic graduated cylinder.

Just got my first pH meter and ran into a question that perhaps someone would care to answer:

How do you store your meter while you are brewing? Is a measuring cup of cool water OK or should I be careful to put it back into the storage solution between mash and sparge?

Puddlethumper said:

Is a measuring cup of cool water OK or should I be careful to put it back into the storage solution between mash and sparge?

Click to expand...

That should be fine.