# PH Pen Storage Fluid



## AverageWhiteBloke (29 Mar 2013)

Just bought myself a ph pen. Wondered whether or not to also order some storage fluid, I notice that on some of the fluids it says not to be used with pens using gel probes. Wondered why the difference?


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## Martin cape (29 Mar 2013)

No it's fine pal. Just so long as it doesn't dry out. Keep it moist in its case it'll be fine.


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## AverageWhiteBloke (29 Mar 2013)

Keep it moist with what though? I heard deionised  water can damage the probe and not sure if any of the chemicals in tap water could cause problems.


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## Martin cape (29 Mar 2013)

Just leave a little water in the end cap. Doesn't matter whether its aquarium or tap water. The pH probe in these pens aren't that sensitive to be affected by tap water. 

The expensive probes that are used in labs are very very sensitive and cost thousands of pounds. They need to e stored in 3M KCl. But these will be fine so long as they don't dry out totally. They have don't have an internal solution. 

Don't worry


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## BigTom (29 Mar 2013)

I've got a enough storange fluid to last me about 10 lifetimes. Can send you some for the cost of postage if you PM me your address.


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## AverageWhiteBloke (29 Mar 2013)

Pm'd so, out of curiosity what happens when these pens are stored before going on sale? How come once they have been wet they need to stay wet but before they can be dry for as long as they want?


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## Martin cape (29 Mar 2013)

Good point. Technically speaking they come pre calibrated so they have been wet before. So they should be kept wet. But like you say, when I got mine it was bone dry. Maybe isn't such an issue with such a "cheap" probe. We are taught never let a pH probe go dry. Basically with the lab ones, the solution inside them evaporates and the sensitive electrode dries out. 

I wouldn't worry with these ones. I've never even rinsed mine, test then put lid back on with it still wet. It's never gone out of calibration yet and had it 2 months.


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## Vanish (30 Mar 2013)

Why use a ph pen. Is this to check Co2 levels.


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## Andy Thurston (18 Apr 2013)

My ph pen came bone dry too it also needed calibrating 3 times in first month. it seems to have settled down now. i have a small piece of cotton wool in lid to hold moisture and keep it wet with tap water now i check it every second week  and its been fine for
3 months with no adjustment


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## Martin cape (18 Apr 2013)

3M KCl is the ideal storage solution if you can make some of that up. Should be able to buy potassium chloride salt from somewhere.


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## Steve Smith (18 Apr 2013)

Any recommendations on a budget PH probe/pen?


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## Martin cape (18 Apr 2013)

eBay pal. Got mine for £9 delivered.


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## Andy Thurston (18 Apr 2013)

Mine came from hydroponics shop for £45 was thinking of ebay route.can get them for as little as £7 but wont have original package this is to reduce shipping costs from china
I think if you test  once a day its money well spent  and their also much less hastle than liquid tests
Be aware that some dont have temereature compensation so you might have to let water get to room temp for accurate reading but this is easily tested by testing at room and tank temp to check difference
Its also worth remembering there not all submersiable  so dont drop it in tank 
Claibration buffers are readily available from ebay  too


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## Martin cape (18 Apr 2013)

I wouldn't worry about temperature difference. Difference of 10 degrees Celsius only has a difference of 0.1 on the pH scale. 

Which is the error on these pens anyway. Readings are always for example, 7.0 +/- 0.1


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## lurch1000 (18 Apr 2013)

So the storage solution is recommended for all types (and prices) of (pH) pens is it?


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## Martin cape (18 Apr 2013)

Will be. They are all basically a glass electrode with the copper wire sensor running through. 

We use either 3M KCl or if out of it pH 7 buffer in the labs.


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## lurch1000 (18 Apr 2013)

Hot given mine with no destructions recently, never gave it a second thought. Sounds like a case for wet cotton wool in the cap!


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## Pinkmummy79 (3 May 2013)

i need to get me one of these pens


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## lurch1000 (4 May 2013)

Here's one on eBay you can look at - http://bit.ly/100XQAQ


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## Andy Thurston (4 May 2013)

Bargain at that price


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## lurch1000 (4 May 2013)

Do a TDS meter for £4 as well, and a combined package of two which is a weird deal.


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## Andy Thurston (8 May 2013)

Not that wierd. tds pens are used to measure purity of ro water which lets you know when membranes need replacing


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## lurch1000 (8 May 2013)

Now I re-read my comment it's ambiguous to say the least.

He does pH pens, he does TDS pens. To buy the two together is a weird deal. The pens separately come to £9, but posted about £16. Together they're £12 and postage makes them £15.


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