Monday, December 27, 2010

Calibrating my pH meter

As I mentioned, my lovely husband and mother bought me a pH meter for Christmas. It's a Jenco Vision Plus and it's quite fancy as it can store up to 50 readings, take temperatures, and many more features I have yet to try! It even comes with a handy dandy belt hook so I can wander around the house testing everything (except I don't own any belts!) But it didn't come with calibration solution!

I could have ordered it from an aquarium supply place or my new favourite shop, Pro-Lab in Quebec (check out the beakers and test tubes!), but I didn't want to wait to play and I wanted to shop local. So I went to one of the many hydroponic growing stores in Chilliwack - thank goodness I live in the grow op belt of B.C.! - and bought myself a container of pH 4 and pH 7 calibration solution. (They didn't have the pH 10, so I will order that from Pro-Lab!)

If you have a pH meter, you'll need some calibration fluid. Mine calls for pH 4, pH 7, and pH 10, although I can get away without the pH 10. Check what you need. You might find it locally at aquarium or hydroponic or "indoor growing" stores. 

Mine called for me to soak the electrode in the pH 4 solution for 10 minutes before using it for the first time. My husband yelled, "Oh boy, Hawaiian punch!" upon seeing the solution! After the 10 minutes, it was time to calibrate it for the first time.

I rinsed it with distilled water, then put it into the pH 7 solution, which was a lovely lime green, until it noted the pH and held it. Then I rinsed it again, then put it into the pH 4 solution until it noted the pH. Calibration done.

I could have done a triple calibration with pH 10 included, but I don't have that yet. I will once I've purchased some! 

Calibration done! Time to get measuring!

Our caramelized onion marmalade has a pH of 3.9! I'm off to the workshop to test more stuff!

As a note, every pH meter is different so check yours to see what the manufacturer suggests. I just wanted to share in the pH meter-y happiness!


Zenobiah said...

Do you have to calibrate it every time you use it or just the first time?

Topcat said...

Okay, I will get my new pH meter out and actually read the instructions I wonder what the pH of my daughter's white chocolate and passionfruit cheesecake is?

Anne-Marie said...

Love your science-minded-brain. =) I have one of those pH meters and calibrated it once like a decade ago so you're definitely bringing back memories.

Susan Barclay-Nichols said...

For my meter, you have to calibrate it the first time with a pH 4 solution, and then every few weeks or so or when you've stored it for a long time. Every meter is different, so you have to read your manual to see what your meter requires!

kontakt said...

Cool! I only know of the very expensive professional lab ph meters, where the electrode is like 1000 US dollars (not kidding here) and the cheap ph papers. I never knew there was inbetweens. I have to get one... some day. (It seems your family knows exactly what you want for Christmas!)

Leman said...

I was wondering if anyone from UK can recommend a pH meter? thanks

inge data said...

This is a great device! I found some more information on this website:

Tom said...

I bought a pH meter but am finding it a bit hit and miss with emulsions... any advice? Is there a particular type of pH meter that works with lotions/creams etc.?


Debbie said...

Love your useful articles and thanks for sharing so much. My question: The end on my pH meter that tests the pH is blunt and had corners and crevices. I don't feel comfortable lowering it into my lotions to test the pH because I lack confidence in cleaning it between uses. Once covered with the lotion the ends are hard to rinse clean.
Are pH meters sold for testing soil which are shown with plain electrodes suitable for lotions. AND how long does the pH meter have to be exposed to the emulsion before the reading is taken.

Susan Barclay-Nichols said...

Hi Debbie. I don't know the answer to your question about using a plant pH meter. Sorry. And the time it takes will depend upon the meter. I remember from chemistry class they suggested about 2 to 3 minutes with the machines there, and it seems to work for my machine, too.

Maron said...

First of all, sorry for my basic english, not my native language.
Second, I'm very curious about your pH meter, is it suitable for viscous samples?
I recently learned in pharmaceutical technology class that you can't read pH with a regular pH meter in a viscous solution, is better do it with a pH band than with a pH meter not suitable for viscous samples.

I really want to know if your pH meter is suitable and if not, why you decide use it anyway? Is there any reason for use it over a pH band? Thanks for your time!
Kind regards!

Susan Barclay-Nichols said...

Hi Maron. Yes, mine is good for viscous samples, although I tend to water down my lotions and surfactants for testing if they are too thick as it makes it harder to clean the sensor.

By pH band do you mean a pH strip? If that is your question, it's because pH strips just aren't accurate enough. They give you a very broad pH range of 1, and for cosmetic chemistry, we need more accuracy.

Stephanie said...

Excellent, this is just what I was looking for as all of the ph meters I've been looking at look really difficult to clean.

So, is it correct then that water will not alter the pH of the sample? Second, how do you actually clean your pH meter. I'm wanting to measure something that is more of a "cream" though still o/w, so quite thick. I'm thinking to remove a sample for testing. That way the meter never actually goes in the batch to be bottled, but I've read on other blogs that yeah, a meter is not accurate in creams. I'll be looking for the exact one you have although it's a bit more than I need. If you say it works in such products, I'll start there.

Also, I've read the temperature will affect the reading. If so, does it need to be below a specific temp? Or room temp. As of course this will also affect my viscosity at the time of reading.

If you could comment on the addition of water (should I use distilled or does it matter)to the test sample and the actual cleaning that would be greatly appreciate as the guy at the hydroponics store strongly advised against using anything other than water to clean it but I don't see how water alone will remove any residue.

Thank you in advance for any and all advice. - If this is already covered somewhere I'd be happy to read where directed. If it is covered in one of your books, I'd be happy to donate to have access to the information.

Thanks again,

Susan Barclay-Nichols said...

Hi Stephanie. If you're using distilled water with a pH of 7, adding lotion to it will give you an accurate reading of pH. You can add something like 10% lotion - so 10 grams lotion to 90 grams of water - and get a good reading of your product. I measure all my products with this pH meter, including lotions and conditioners, and I feel confident about the results.

Mine works well at room temperature, so let your products cool and measure it then. My meter has a temperature gauge on it, but make sure you get the right one for where you live. Mine is in Farenheit and it drives me nuts as I'm a metric girl!

I wash mine with a little gentle surfactant blend I make up with decyl glucoside and cocamidopropyl betaine, but then again, my sensor doesn't say I can't wash it with surfactants. I use a really dilute solution of it - maybe 2% or so in the water - and wash it with a gentle cloth. We wash the pH meters in the lab at school, so maybe you just need to find a different one?

I hope this helps!