How to Calibrate and use the pH Meter?



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How to Calibrate and Use a pH Meter

Three Parts:

Chemists, biologists, environmentalists, and lab technicians alike all use pH to measure the acidic and basic potentials of a solution. A pH meter is very useful and the most accurate tool available to test pH levels. There are many simple steps, from preparing your materials to methodically calibrating and testing, to ensure you have the most accurate reading of pH levels possible.

Steps

Preparing for Calibration

  1. Turn on your pH meter.Before you begin to calibrate and use your pH meter you will first need to turn it on and allow adequate time for the meter to warm up. This should generally take around 30 minutes, but check your pH meter’s operating manual for exact times.
  2. Clean your electrode.Take the electrode out of its storage solution and rinse it with distilled water under an empty waste beaker. Once rinsed, blot dry with Kimwipes or Shurwipes, which are available at most office supply stores.
    • Be sure to rinse your electrode in a waste beaker that is different from the beaker you will be calibrating in.
    • Avoid rubbing the electrode as it has a sensitive membrane around it.
    • If you find the electrode to be particularly dirty consult your operating manual for recommended cleaning solutions.
  3. Prepare your buffers.You will generally need more than one buffer for calibrating a pH meter. The first will be a “neutral” buffer with a pH of 7, and the second should be near the expected sample pH, either a pH of 4 or 9.21. Buffers with a higher pH (9.21) are best for measuring bases, whereas buffers with a low pH (4) are best for measuring acidic samples. Once you have chosen your buffers allow them to reach the same temperature as the pH meter because pH readings are temperature dependent. Pour your buffers into individual beakers for calibration.
    • Check with your pH meter manufacturer, or current educational or professional institution, about acquiring pH buffer solutions.
    • Buffers should be kept in a beaker for no longer than two hours.
    • Discard the buffer when you are finished. Do not return it to its original container.
Score
/

Part 1 Quiz

What pH should your first buffer have?

Calibrating Your pH Meter

  1. Place your electrode in the buffer with a pH value of 7 and begin reading.Press the “measure” or calibrate button to begin reading the pH once your electrode is placed in the buffer.
    • Allow the pH reading to stabilize before letting it sit for approximately 1-2 minutes.
  2. Set the pH.Once you have a stable reading, set the pH meter to the value of the buffer’s pH by pressing the measure button a second time. Setting the pH meter once the reading has stabilized will allow for more accurate and tuned readings.
    • Although not necessary, if you stir your buffer before measuring be sure to stir all other buffers and samples in the same way.
  3. Rinse your electrode with distilled water.Rinse and pat dry with a lint-free tissue, like Kimwipes or Shurwipes, in between buffers.
  4. Place your electrode in the appropriate buffer for your sample and begin reading.Press the measure button to begin reading the pH once your electrode is placed in the buffer.
  5. Set the pH a second time.Once your reading has stabilized, set the pH meter to the value of the buffer’s pH by pressing the measure button.
  6. Rinse your electrode.You can use distilled water to rinse. Use a lint-free tissue, like Kimwipes or Shurwipes, in between buffers to dry the electrode.
Score
/

Part 2 Quiz

When you place the electrode in the buffer with a pH of 7, how long should it take for the pH to stabilize?

Using Your pH Meter

  1. Place your electrode in your sample and begin reading.Once your electrode is placed in your sample, press the measure button and leave the electrode in your sample for approximately 1-2 minutes.
  2. Set your pH level.Once the reading has stabilized, press the measure button. This is the pH level of your sample.
  3. Clean your electrode after use.Rinse your electrode with distilled water and blot or dab dry with a lint-free tissue. You may store your pH meter once clean and dry.
    • Consult your operation manual for optimal storage practices for your specific pH meter.
Score
/

Part 3 Quiz

How should you clean the electrode after use?

Community Q&A

Search
  • Question
    How do I discuss the pH meter calibration report when writing a standard operation procedure?

    M.A. in Environmental Science and Management
    Bess Ruff is a Ph.D. student of Geography in Florida. She received her M.A. in Environmental Science and Management from Bren School of Environmental Science & Management, UC Santa Barbara in 2019.
    M.A. in Environmental Science and Management
    Expert Answer
    This article provides a solid outline for how you should write up the calibration steps in any formal lab report. You'll want to be sure to mention which buffer you used and why as well as the temperature of all components involved.
    Thanks!
  • Question
    Is it always necessary to calibrate the pH meter before using?
    wikiHow Contributor
    Community Answer
    Usually daily calibration is necessary.
    Thanks!
  • Question
    My Jellas pH meter recommends calibrating with deionized water. Is deionized water necessary, or can distilled water be used?
    Michael Li
    Community Answer
    Deionized water basically means water without any ionic charges. It requires ion exchangers to perform the process. However, distilled water will work fine.
    Thanks!
  • Question
    What are the disadvantages of a pH meter?
    wikiHow Contributor
    Community Answer
    Nothing! They are great!
    Thanks!
  • Question
    What are negatively charged H atoms?
    Aussie J
    Community Answer
    They are hydrogen ions - basically a free-floating hydrogen atom regarded as negatively charged, as it has gained an electron to have a stable outer shell.
    Thanks!
  • Question
    What is a pH meter?
    wikiHow Contributor
    Community Answer
    It measures the potential usable amount of free moving hydrogen atoms versus the amount of available negatively charged protons. More hydrogen = acidic = pH number less than 7. More protons = basic = pH number greater than 7.
    Thanks!
  • Question
    How can I calculate the slope of pH meter manually from pH value?
    wikiHow Contributor
    Community Answer
    I think this is the correct answer, but still you can verify. A good electrode has a mV of 0 ± 30 mV in pH 7. The slope should be 90 to 105%. For example: Readings pH 4 : 4.29; pH 7 : 7.43. Convert pH 7 reading to mV. 7 – 7.43 = -0.43 pH * 59.16 mV/pH = -25.44 (this value is okay because it is within 0 ± 30mV). Convert pH 4 reading to mV. 7 – 4.29 = 2.71 pH * 59.16 mV/pH = 160.32. Calculate slope: 160.32 – (-25.44) = 185.76 mV/ 177.48 mV * 100 = 105 % (this value is borderline as 105% is the upper limit).
    Thanks!
  • Question
    What are the fewest counts required during calibration?
    wikiHow Contributor
    Community Answer
    I usually do 2 to 3, but I guess you would be okay doing 1.
    Thanks!
  • Question
    What should I see when turning on the pH meter?
    wikiHow Contributor
    Community Answer
    The pH meter should be on as indicated by the visual display, but the specifics will vary by model. If the power does not come on, contact the pH meter manufacturer.
    Thanks!
Unanswered Questions
  • How do I a calibrate pH meter for testing sauce at a particular temperature?
  • Can you and do you need to calibrate the temperature compensation probe of the pH meter?
  • How much naoh is required for calibration?
  • Short note for operating pH meter?
  • What are procedures can be followed during the calibrating pH meter?
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  • Be sure to always ask questions if you are unsure about a process. Ask your supervisor in your lab or consult your operator’s manual at home.
  • All pH meters are a little different. Check all necessary manuals before starting to calibrate and use your pH meter.

Warnings

  • Follow all other set safety regulations when working with hazardous samples.

Things You'll Need

  • pH meter
  • Distilled water
  • Kimwipe or Shurwipe, a special thin tissue specifically for laboratory use
  • pH 9.21 buffer, a solution whose pH is constantly 9.21
  • pH 7 buffer, a solution whose pH is constantly 7
  • pH 4 buffer, a solution whose pH is constantly 4

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Date: 07.12.2018, 11:53 / Views: 42134