pH Measurement of Agar Media | METTLER TOLEDO
Application Editorial

pH Measurement of Agar

Application Editorial

Accurately Measure the pH of Agar Media Using a Specialized Sensor

To learn more about measuring the pH in agar media download this free application note
To learn more about measuring the pH in agar media download this free application note

Measuring the pH of agar media is challenging when using a routine pH sensor. The flat surface and solid gelatinous nature of agar plates results in inadequate contact between the sample and the sensor, – when a sensor with a spherical pH sensing membrane is used. The result is an improper interaction between the sample and the reference electrolyte. Both of these factors are major limitations of traditional sensors and cause readings to fluctuate while measuring the pH of agar media. Such challenges could be overcome by using a sensor with a flat surface pH membrane such as the InLab Surface Pro-ISM.

METTLER TOLEDO's InLab® Surface Pro-ISM is a specialized sensor with a low resistance glass membrane that ensures improved accuracy and faster response times. It has a flat pH sensing membrane allowing the junction to have complete contact with the sample while measuring. The sensor also has an open ceramic ring junction that allows for faster outflow of the reference electrolyte, thus reducing the measurement delay. The InLab Surface Pro-ISM sensor is especially designed to be the ideal sensor for measuring the pH of flat surfaces like agar media.

To learn more about the benefits of using a specialized sensor like the InLab Surface for measuring the pH in agar media, download our free application note.

The following sections highlight more details about agar as a nutrient media and discusses the importance of measuring its pH.


What is an agar media?

Agar media consists of a solid gelatinous polymer forming the solid base. It is often mixed with appropriate nutrients in the right proportion to form a solid growth medium favorable for culturing micro-organisms.


Why is measuring the pH of agar media important?

Apart from the complete nutritional composition, stable pH becomes vital for optimum microbial growth in culture media. The pH of a culture medium provides favorable H+ ion concentration suitable for the growth of microorganisms. The enzymes present within the bacteria are affected by pH. The alteration of pH causes their denaturation and also brings about an alteration of the ionic charges on the molecule. Usually, the catalytic properties of the enzymes are lost and metabolism is halted. This has an adverse effect on the microbial growth despite the presence of nutrient rich medium.


What is the optimum pH for growing the micro-organisms?

Most bacteria grow around pH, which is near neutral and in the range of 6.5 to 7.0. We may also encounter some bacteria called acidophiles, which live in an acidic environment with pH values as low as 1.0.


To learn more about the importance of pH measurements in agar media, advantages of using the right sensor and good measuring practices, download our application note by clicking on the button above.

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