Author Topic: PH Meter 101  (Read 781 times)

Offline flbrewer

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PH Meter 101
« on: July 08, 2015, 12:26:28 AM »
I have a PH meter coming tomorrow, and MoreBeer does a pretty good job of providing the below 101 information. Anything else I need to know or watch out for?

http://www.morebeer.com/public/pdf/wphmeter.pdf

*Thanks for the read if you look through this.

Offline pfabsits

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Re: PH Meter 101
« Reply #1 on: July 08, 2015, 07:36:17 PM »
I would be curious as to what meter you purchased and why? Where you looking for a particular feature (auto cal, ATC), price, or brand preference.

Couple of tips for use:
1) If you will use frequently (3-4X/week) then buy bottles of buffer. Since readings will be on the acid side (<pH 7) then I would recommend calibrating to pH 7 then pH 4. If you will be using the meter 1-2X/month then I would go with the packets of buffer. A box of 25 packets of pH 7.0 will run around $20. With bottles they should be changed about every 6 months after opening. The packets are fresh every time they are opened. Calibration is only as good as the buffer.

2) Use storage solution. The solution is used to keep the pH indicating bulb and junction hydrated.A pH probe generates a voltage in a solution.  The voltage generated in a buffer by a probe that is properly hydrated is different than one that is dry. A thin hydration layer forms on the bulb after about 3-4 hours of sitting in a solution. If you are using a tester (pen type) then take a small piece of sponge from kitchen scotch scrubbing pad and place in the protective cap that covers the electrode. The storage solution can be used to wet the sponge. The wet sponge will maintain the hydration layer. Another option is to place a small amount of storage solution into a small glass that the meter is placed into. There only needs to be enough solution to cover the bulb and junction. If you do not have storage solution then use pH 4 buffer. If you do not have pH 4 then use pH 7. NEVER USE DISTILLED WATER TO STORE.

3) Use purified water (distilled, reverse osmosis, deionized) to rinse the electrode before and after placing in a solution (buffers, sample, storage). If you do not have purification equipment the water can be purchased from any grocery store. For example Aquafina is purified by reverse osmosis.

4) For most standard pH electrodes it is important to not use at elevated temperatures. High temperatures > 140-150 oF will shorten the life of the electrode. It is better to allow a sample to cool before taking a measurement. The rule of thumb is that at 25 oC a probe will last 1-2 years. Every 25 oC increase will cut the life in half. There are pH electrodes made with glass rated for high temperatures. They tend to be more specialized.

The one thing to do when you get the meter is to allow the probe to hydrate. If possible let stand overnight in a solution before using. That way you will know that he probe is properly hydrated. If you want to see the effect of hydration then take a pH reading when you get the meter and then take another the next day. The difference is the error associated with hydration. Do not worry about calibration just look at the relative difference. It should be around 0.1 to 0.2 pH. The response will also be more sluggish when the probe is dry. After the probe is hydrated then do the calibration.

Please feel free to ask if you have any questions. As an instrumentation manufacturer we are truly concerned that you are comfortable in the proper use of a meter. Regardless of brand. Just send a message or post on this topic.
One of the avid home brewers that work for Hanna Instruments

Offline klickitat jim

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Re: PH Meter 101
« Reply #2 on: July 08, 2015, 09:19:47 PM »
Thanks for all that info! I'm new to pH meters too and learning and relearning really helps.

Offline mabrungard

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Re: PH Meter 101
« Reply #3 on: July 09, 2015, 10:50:59 AM »
I echo the caution against measuring high temperature liquids.

Yes, there are special pH probes that are optimized for operating at high temperatures approaching 200F. However, those probes are for continuous processes and the probe is kept at that hot temp for essentially its whole life. That is far from the intermittent hot/cold/hot/cold that a probe will see in the brewery. Even if you left the probe in the mash the whole time, it would only be a hour or so and then its cooling off. It is primarily the cycles of temperature change that destroy the probe. For brewers, it is impossible to keep a probe at a constant high temperature. For that reason, it is best to keep the probe and the solutions it measures at a relatively consistent near-room temperature.

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Offline flbrewer

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Re: PH Meter 101
« Reply #4 on: July 12, 2015, 05:41:34 PM »
Anyone know what these white crystals are on my new PH meter?

Offline pfabsits

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Re: PH Meter 101
« Reply #5 on: July 12, 2015, 06:45:25 PM »
The white crystals are salt from inside the reference portion of the pH electrode. Every reference cell has a junction (porous barrier between inside the cell and the solution being measured) that small amounts of salt diffuse out from inside the electrode. It is normal and shows that the junction is not clogged. Just rinse off with some water before use.
One of the avid home brewers that work for Hanna Instruments

Offline flbrewer

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Re: PH Meter 101
« Reply #6 on: July 13, 2015, 12:59:56 AM »
Side question...is the storage solution and 4.0/7.0 calibration solution safe to handle? Just trying to be ultra safe w the newborn in the house.

Offline klickitat jim

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Re: PH Meter 101
« Reply #7 on: July 13, 2015, 02:52:36 AM »
Dunno that I would drink it or rub it in my eyes, but 4.0 is less acidic than sour beer and 7.0 is like distilled water, non acidic or basic

Offline pfabsits

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Re: PH Meter 101
« Reply #8 on: July 13, 2015, 12:53:45 PM »
The buffers should be non-hazardous. The MSDS (Material Safety Data Sheets) can usually be found on the manufacturer's website. From one site pH 4 is listed:
http://www.hannainst.com/sds/SDS_HI%207004_2013-04-01.pdf

SECTION 2:
HAZARD IDENTIFICATION
Non-hazardous product as specified in Directives 67/548/EEC and 1999/45/EC.
Non-hazardous product as specified in OSHA Regulation 29 CFR 1910.1200.
Non-hazardous product as specified in Canadian Regulation SOR/88-66.
Non-hazardous product as specified in Regulation (EC) 1272/2008.

SECTION 4:
FIRST AID MEASURES
After Inhalation: Remove to fresh air. Call a physician if breathing becomes difficult.
After Skin Contact: Wash affected area with water and soap.
After Eye Contact: Rinse out with plenty of water for at least 15 minutes. If pain persists, summon medical advice.
After Swallowing: Wash out mouth with plenty of water, provided person is conscious. Obtain medical attention if feeling unwell.

The statements above are general statements. To put it in perspective all pH probes are calibrated in buffers and in the food industry placed in food after calibration. Ultimately, if a child consumed some buffer then it would be recommended to download the MSDS and contact a medical professional.

Use the link below to see what typical chemicals are used in making a pH buffer. The chemicals listed are what are purchased to validate a pH buffer (NIST traceable). For example pH 4 has potassium hydrogen phthalate.

http://www.nist.gov/srm/upload/SP260-53.PDF

One of the avid home brewers that work for Hanna Instruments