Author Archives: ssiNadmin

pH Electrode Storage

 

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So, you have a new pH electrode? Let’s talk about what we can do every day to keep it in shape. Which reminds me… Why did the acidic water go to the gym? Because it wanted to be a buffer solution.

The first thing you need to know is that the glass bulb on the end of your pH electrode is a very thin semi-permeable membrane. Which means it needs to stay clean, so that the small channels in it don’t get clogged. Also, you don’t want to touch it with much or it may break. The next thing you need to know is that it should be kept wet – and a beaker of water just isn’t going to do.

Some people try storing the electrode between readings in clean distilled or deionized water, but these waters have a lack of ions and tend to be relatively non-conductive. You see, water is actually not conductive to electricity. It is the free ions, such as the dissolved minerals and other things in the water that makes it conductive. pH is a type of measurement of the charge of the free Hydrogen or Hydroxyl ions. But measuring pH is impossible if the electrode or the solution is not conductive. So, storing your electrode in distilled or deionized water leaves your electrode unable to make any readings because all of its conductive ions have been diluted away.

Some people try tap water, but the minerals and eventually the growth of algae and mold can clog the electrode. A dirty electrode can often be very slow to stabilize. If it becomes completely clogged, we will have the same non-conductive situation we did with distilled water, and readings will become erratic.

Many people use buffer standards, like 4, 7, or 10 to store the electrode, but these buffers will make the pH electrode tend to read the pH of the buffer it was stored in. So if you store the electrode in a 7 it will tend to read acidic readings high and basic readings low. For example, a pH of a 5.8 might be read as a 6.4 if the electrode was stored in pH 7 buffer.

The electrode filling solution would be great to store the electrode in, but as it evaporates it will leave the salt crystals behind and make a mess. So the only real solution (pun intended) is to use electrode storage solution. Some storage solutions are just buffers with extra salt, so be sure to call LabtronX to get the scoop on the choices we provide our customers, including our own LX pH Storage Solution.

Temperature effects on pH readings

 

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During the course of a year, the temperature of your pH samples can vary dramatically. Whether you’re as hot as a sweating stormtrooper on Tatooine, or Luke-warm in a tauntaun on Hoth, how can you be sure your pH measurements are correct?

A water molecule is described in chemistry as H2O or HOH. We could say it is made up of two Hydrogen atoms and one Oxygen atom. But it’s probably more correct to say it is made up of Hs and OHs. You see, pH is the indirect measurement of the ratio of free Hydrogen ions (H) versus free Hydroxyl ions (OH).

To help us understand this, let’s go to a galaxy far, far away. Let’s use the darkside’s Imperial stormtroopers to represent the Hs in the solution and Rebel pilots to represent the OHs in the solution. We can easily see that if there are more rebel pilots on a given planet than there are stormtroopers this must be the location of the rebel base – more OHs in a solution is a “basic” solution. Obviously, going the other way, when the darkside takes over it is a very “acidic” situation.

Now, adding temperature to the equation is quite simple. The planet’s weather conditions have very little to do with the actual ratio of rebels to stormtroopers. However, on a cold planet like Hoth, it’is difficult to count the forces present, because they are dormant in their ice caves trying to stay warm. On a warm planet like Tatooine, everyone is swimming at the pool trying to stay cool. With the right equipment, they are easy to count from orbit in your Corellian cruiser.

In terms of pH, the pH does not change with temperature – only the pH reading. And this pH reading is changed with temperature because of activity of the ions which affects our electronic equipment. To avoid inaccurate readings, there are three simple practices to incorporate into your pH measurements. 1) Automatic temperature compensation (ATC) should be used in the form of a separate probe, built into the pH electrode (triode), or by entering the temperature into the meter manually. 2) If you have auto-buffer recognition, you must be sure to use the correct buffers for that meter, so that the setpoint for any given temperature is correct. 3) Try to avoid large differences in temperature between your calibration buffers and your water sample when possible.

Always remember, unstable or inaccurate pH readings could be caused by unstable or inaccurate temperature readings. And… may the pHorce be with you.

Man tries to Calibrate Kleenex… The story at 11.


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Roger and Betty had been married over 40 years and he loved her very much. Throughout their relationship, she was always doing nice little things for him. Every morning, for over 40 years, Betty would put a Kleenex into each of his two work shirt pockets just in case he needed them. Sadly, after Betty died, Roger was left to take matters in his own hands.

Have you ever noticed how we use words incorrectly by giving them larger meanings than they’re supposed to have? Kleenex is a brand name of facial tissue that was originally marketed in 1924 as a way to remove cold cream. Kleenex is now synonymous with any brand tissue used to blow one’s nose.

Even though there are only 97 men for every 100 females in the US, we still use the word “he” as a generic pronoun to describe people. And the word “man” is used to describe our race even though there are actually 10% more women in the world than their masculine counterparts.

The use of the word “calibration” is much the same. Calibration is actually the act of adjusting an instrument to measure a primary standard within a certain tolerance. Normally this standard is certified, and the calibration is said to give this instrument traceability to the certified primary standard.

Calibration is also used generically to describe the process of “verification.” Verification is a way of confirming that an instrument can make a measurement within a set tolerance. Often this can be done with the use of secondary standards on a more regular basis. If the verification fails or is just within tolerance, then there may be a need for calibration.

What do we do with glass thermometers? Because there are no adjustments, you cannot calibrate a thermometer. You can verify its reading by comparing it to a temperature standard and see that it reads within tolerance. But what do you do if it is out of tolerance? You note the deviation from the true reading and “standardize” the thermometer by assigning a correction factor. This correction factor is used to add or subtract from the reading you get to obtain the true temperature reading.

So, when your equipment has been “calibrated,” it may have been calibrated, verified, or standardized. No doubt, there are probably many other processes that end up being called calibration. But unlike Roger you don’t need to take matters into your own hands, you have LabtronX to help.