pH meter probe shelf life, and pH paper

pH meter probe shelf life, and pH paper

Post by Richard Kova » Sun, 21 Oct 2001 02:24:37



I just purchased a "Checker 1" pH meter.  Judging by the packaging and
the dust on it, I'm guessing it's been on the shelf at the store for
at least a couple of years.  Do the probes on these have a limited
shelf life?  Do I need to be concerned that it's already past it's
prime?  How do you know when the probe is no longer any good?

I also purchased buffering solutions to calibrate it -- from a better
store, so I'm pretty confident the solutions were quite new (this
store was sold out of meters though, and their supplier was
back-ordered).  It took quite a lot of adjustment, but it did
calibrate.  About 12 hours later I wanted to measure again.  The
reading was about as expected, but I thought I should calibrate again
just in case.  Unfortunately my 4.0 solution seemed to be way off -- I
couldn't get the meter to go down lower than 4.6, even though it was
reading about 3.6 in the wine sample.  Is 4.0 buffer solution normally
that sensitive?  It was just a ***y little bottle, so I was inserting
the meter right into the bottle (rinsing well before and after).  I'm
really puzzled that it seems to have gone that far out so quickly -- I
was pretty careful to seal the bottles as soon as I was done any
readings.

Finally, I've seen many comments about pH paper not being accurate
enough for winemaking.  Does this also apply to narrow-range pH paper
that is specifically for wine (I think it's for around 3.0 to 4.6 or
something)?  My new (old?) meter seems to read about the same as the
pH paper I've got, and my narrow-range pH paper readings seem to be in
the same accuracy range (.1 or .2) that the meter is rated for...

Thanks for your help!

Richard

 
 
 

pH meter probe shelf life, and pH paper

Post by J Reite » Sun, 21 Oct 2001 22:45:52


Richard,
   soak the probe in buffer 7 for a whole day. Then calibrate and see where
it goes. The trick to probe life is how well you keep them hydrated. If
there is a cap on the end of the probe you can keep that filled with buffer
7. It can be a bother, but check your pH meter a few times a year, not just
at harvest time.
Joanne


Quote:
> I just purchased a "Checker 1" pH meter.  Judging by the packaging and
> the dust on it, I'm guessing it's been on the shelf at the store for
> at least a couple of years.  Do the probes on these have a limited
> shelf life?  Do I need to be concerned that it's already past it's
> prime?  How do you know when the probe is no longer any good?

> I also purchased buffering solutions to calibrate it -- from a better
> store, so I'm pretty confident the solutions were quite new (this
> store was sold out of meters though, and their supplier was
> back-ordered).  It took quite a lot of adjustment, but it did
> calibrate.  About 12 hours later I wanted to measure again.  The
> reading was about as expected, but I thought I should calibrate again
> just in case.  Unfortunately my 4.0 solution seemed to be way off -- I
> couldn't get the meter to go down lower than 4.6, even though it was
> reading about 3.6 in the wine sample.  Is 4.0 buffer solution normally
> that sensitive?  It was just a ***y little bottle, so I was inserting
> the meter right into the bottle (rinsing well before and after).  I'm
> really puzzled that it seems to have gone that far out so quickly -- I
> was pretty careful to seal the bottles as soon as I was done any
> readings.

> Finally, I've seen many comments about pH paper not being accurate
> enough for winemaking.  Does this also apply to narrow-range pH paper
> that is specifically for wine (I think it's for around 3.0 to 4.6 or
> something)?  My new (old?) meter seems to read about the same as the
> pH paper I've got, and my narrow-range pH paper readings seem to be in
> the same accuracy range (.1 or .2) that the meter is rated for...

> Thanks for your help!

> Richard


 
 
 

pH meter probe shelf life, and pH paper

Post by Dewey & Lucy Thompso » Tue, 23 Oct 2001 05:26:41


Richard, comments embedded below.

Quote:
> I just purchased a "Checker 1" pH meter.  Judging by the packaging and
> the dust on it, I'm guessing it's been on the shelf at the store for
> at least a couple of years.  Do the probes on these have a limited
> shelf life?  Do I need to be concerned that it's already past it's
> prime?  How do you know when the probe is no longer any good?

No, the probe should be fine.  If it is stored properly it should last for
years. Get some pH probe storage solution, KCl.  In a pinch you can use
buffer 7, but KCl works better.  You will know when the probe is toast.  It
will be very flakey.......

Quote:
> I also purchased buffering solutions to calibrate it -- from a better
> store, so I'm pretty confident the solutions were quite new (this
> store was sold out of meters though, and their supplier was
> back-ordered).  It took quite a lot of adjustment, but it did
> calibrate.  About 12 hours later I wanted to measure again.  The
> reading was about as expected, but I thought I should calibrate again
> just in case.  Unfortunately my 4.0 solution seemed to be way off -- I
> couldn't get the meter to go down lower than 4.6, even though it was
> reading about 3.6 in the wine sample.  Is 4.0 buffer solution normally
> that sensitive?  It was just a ***y little bottle, so I was inserting
> the meter right into the bottle (rinsing well before and after).  I'm
> really puzzled that it seems to have gone that far out so quickly -- I
> was pretty careful to seal the bottles as soon as I was done any
> readings.

No, the buffer solution is very difficult to ruin, however I would suggest
that you use a small secondary sample beaker, I use a contact lense storage
case.  It has two sides, and they are small enough that you use only a few
mLs of solution.  It is a "bad lab practice" to actually use the original
container.

Quote:

> Finally, I've seen many comments about pH paper not being accurate
> enough for winemaking.  Does this also apply to narrow-range pH paper
> that is specifically for wine (I think it's for around 3.0 to 4.6 or
> something)?  My new (old?) meter seems to read about the same as the
> pH paper I've got, and my narrow-range pH paper readings seem to be in
> the same accuracy range (.1 or .2) that the meter is rated for...

The only beef I have with the narrow range pH papers is trying to read red
wine.........For white they work ok.

dewey

 
 
 

pH meter probe shelf life, and pH paper

Post by Richard Kova » Fri, 26 Oct 2001 04:40:09


Quote:

> Richard,
>    soak the probe in buffer 7 for a whole day. Then calibrate and see where
> it goes. The trick to probe life is how well you keep them hydrated. If
> there is a cap on the end of the probe you can keep that filled with buffer
> 7. It can be a bother, but check your pH meter a few times a year, not just
> at harvest time.
> Joanne

Thanks Joanne.  I found similar instructions on Hanna's (manufacturer)
website.  After a few days soaking in buffer 7, the meter seems to
*generally* be working OK.

I also would like to add that I'm extremely impressed with Hanna
customer service -- I posted my concerns on their website on the
weekend, and I had a call from someone before 10am Monday morning.
They suggested I try a few things with both my meter and the retailer,
but ultimately seemed very willing to make sure I had a product that I
was happy with.  Top notch!!!

However, there are still 2 strange things going on that hopefully
someone can help me with:

(a) Usually the meter calibrates fine and will quite quickly zero in
on the buffered solutions and not drift.  But occasionally, the meter
will suddenly jump to a different value (about 1/2 to 1 pH units
lower).  I have to recalibrate, and always within a few minutes it
will just as suddenly jump back to the original range and I have to
recalibrate again (grrrr...)  This "jump" seems to happen only while
testing must or wine.  Is this an indication of a possible bad probe,
or is it and indication of having some CO2 or some other gas or
something in the must that is screwing up the readings?

(b) The meter seems to read fine and steady on 4.0 and 7.0 solutions,
but on my wine/must it seems to zoom down to what I think is the
proper reading (around 3.5 for my grape must, 3.8 for my kit wine) and
then immediately and steadily drifts up-up-up...  It just keeps on
climbing (I usually get tired of watching it when it gets into the
high 4.'s...)  The lowest readings it gives are around what my
narrow-range pH paper indicates and what I expect based on TA
titrations and taste.  Is this behaviour also caused by something in
the must?  Do I need to be heating and cooling the must or doing
something else to it in order to get stable readings?  Generally
speaking, everything I've measured is either pre-fermentation must or
wine that has been bulk aged for at least a couple of months, so I
don't think it should have much if any gas-producing activity going on
in it...

Thanks!

Richard

 
 
 

pH meter probe shelf life, and pH paper

Post by Dave Pik » Sun, 28 Oct 2001 05:53:10


Quote:
> (b) The meter seems to read fine and steady on 4.0 and 7.0 solutions,  but

on my wine/must it seems to zoom down to what I think is the proper reading
(around 3.5 for my grape must, 3.8 for my kit wine) and
Quote:
> then immediately and steadily drifts up-up-up...  It just keeps on

climbing (I usually get tired of watching it when it gets into the high
4.'s...)

This describes what my PH meter has started doing. Even after a lengthy stay
in the buffer solution. Is my meter bad? going bad? or having a bad day?

 
 
 

pH meter probe shelf life, and pH paper

Post by Chopsl » Sun, 28 Oct 2001 09:14:12



Quote:
> > (b) The meter seems to read fine and steady on 4.0 and 7.0 solutions,
but
> on my wine/must it seems to zoom down to what I think is the proper
reading
> (around 3.5 for my grape must, 3.8 for my kit wine) and
> > then immediately and steadily drifts up-up-up...  It just keeps on
> climbing (I usually get tired of watching it when it gets into the high
> 4.'s...)

> This describes what my PH meter has started doing. Even after a lengthy
stay
> in the buffer solution. Is my meter bad? going bad? or having a bad day?

How old is your electrode?  They usually need to be changed every 6 months
or so.  Drifting is usually an indicator.
 
 
 

pH meter probe shelf life, and pH paper

Post by Cari » Sun, 28 Oct 2001 11:03:17


<< > > then immediately and steadily drifts up-up-up...  It just keeps on

Quote:
> climbing >>

pH meter readings WILL drift after about a minute.  Many meters, esp. benchtop
models, will show you when the reading is stable (after about a minute after
putting the electrode into the wine) and shortly thereafter you will get drift
- so you have to watch the meter during the process and take your reading when
exactly when it wants you to.  If you wander off for a cuppa joe you're not
gonna get the readings accurately.
Are you keeping the electrode in the proper electrode solution?  (do NOT use ph
buffer)
Are you rinsing it and blotting it dry BEFORE you put it into the wine?  And
rinsing and blotting it immediately after?  I have worked with pH meter
electrodes for a year plus with excellent results, but you have to maintain
them.  My pH meters, however, are not the little handheld ones made for field
use - I would bet you need to change probes on those every year at least.

Caris
www.lightcatcher.com

"It's a drum and arms waving.
It's a bonfire at midnight on the top edge of a hill,
this meeting here with you."
                                                                        Rumi