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PH measurement issues and solutions

2024-01-09 14:52

Do two measurements of the same sample have different pH values?

Changes in temperature or chemical reactions occurring in the sample itself can cause changes in pH value. Therefore, it is advisable to maintain consistent temperature and avoid chemical reactions.

The same sample was measured on two pH meters simultaneously, but the readings were inconsistent

Due to different calibration conditions between the two pH meters (such as calibration performed at different times), there may be differences in the measured values. So the pH meter needs to be calibrated with the same buffer at the same time, and then measured simultaneously.

No matter what sample the electrode is in, the display remains unchanged?

1. Because the electrode is not truly connected to the instrument. The solution is to first shut down the device and then reconnect the electrodes and instrument.

2. Because the electrode is damaged, it is necessary to replace it with a new one in a timely manner.

Measurement is unstable and takes a long time

1. Due to electrode aging. The response time of the electrode in the buffer solution can be tested. If it exceeds 1 minute, the electrode needs to be activated or replaced with a new one.

2. If the response time of the measurement buffer is short but the measurement sample is unstable, it indicates that the electrode is not suitable for measuring the tested sample. Please choose the appropriate electrode according to the electrode selection guidance.

The sample temperature is 10 ℃, and the instrument displays the pH value at 10 ℃ or 25 ℃

The acidity meter displays the pH value of the solution at the current temperature; If measured at 10 ℃, the instrument displays the value of the solution at 10 ℃; If a pH of 25 ℃ is required, the solution temperature must be raised/lowered to 25 ℃ before measurement.

Calibration issues

Why does the electrode display 702 after calibration in a pH 700 buffer?

At this time, the buffer temperature is around 20 ° C. Due to the slight temperature variation of the pH value of the buffer, 700 is only the value of the buffer at 25 ° C, while the value of the buffer at 20 ° C should be 702. The Mettler Toledo pH meter can automatically compensate for the impact of temperature on the buffer solution to ensure measurement accuracy.

Error or inability to correct the second point during calibration

Due to withdrawal from calibration midway. During the calibration process, simply press the "Cal" key and do not touch any other keys, otherwise the calibration program will exit.

What should be done when the correction slope is greater than 105%?

Check if the buffer has expired. If it expires, replace it with a new buffer solution.

Why has the buffer deteriorated within its validity period and cannot be used?

The shelf life of buffer solution refers to the storage period when it is not opened for use. Once opened and used, the buffer solution is prone to spoilage due to the effects of various fungi in the air.

Attention: Do not pour the used buffer back into the original bottle!

How long is the shelf life of Mettler buffer solution?

The shelf life of 200/401/700/921/1000pH buffer solution and 1413uS/cm, 1288mS/cm conductivity standard solution is 2 years; The pH buffer with three digit accuracy and 84uS/cm conductivity standard also have a shelf life of 1 year.

The validity period refers to the storage period in unopened use. Once opened for use, it is prone to spoilage due to the effects of various fungi in the air. Suggestion: After opening the buffer, put it in the refrigerator to cool down

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