pH Measurement of Liquid Culture Media

pH Measurement of Culture Media. Culture media is a complex matrix that supports the growth and survival of microorganisms. In addition to right nutritional composition, a correct and stable pH is a key to optimum microbial growth in culture media. Growth media can be solid, semi-solid or liquid in nature. The different forms of media present different challenges. pH measurement of solid media is difficult with conventional sensor due to its spherical shape. Since the reference junction is not in contact with the sample, it leads to inaccurate or unstable results. The ceramic junction of pH electrode can be clogged due to complex sample matrix of liquid media. In conventional pH electrode there are free silver ions in the reference system that can leach into the sample and give unstable readings. They could also react with proteins from the sample and precipitate resulting in clogging of the reference junction. The Mettler Toledo solutions to these challenges are specialist sensors like in-lab surface pro is m for solid media and in-lab max pro is m for liquid media The InLab Surface Probe ISM with a flat pH membrane of low resistance LOT glass and ceramic ring junction is ideal for measuring flat surfaces like auger plates. This junction provides fast outflow of electrolyte to enhance response time. The polysulfone shaft ensures good chemical and mechanical resistance. Inlab Max Pro ISM has an immovable glass sleeve junction, which is easy to clean and ensures steady outflow of the electrolyte, enhancing the response time for the measurement in liquid media. The pH-sensitive H.A. glass membrane is extremely robust and ensures reliable results in alkaline media samples. Both sensors have argentthal reference system which consists of AgCl granulated filled cartridge. The silver ion trap arrests the discharge of silver ions into the electrolyte solution and thus prevents the precipitation with proteins in the sample. This gives stable and fast results. The built-in temperature probe, together with automatic temperature compensation functionality of METTLER TOLEDO pH meters, compensates the temperature effects by measuring sample temperature accurately. These sensors have an intelligent sensor management, or ISM, technology that offers data security by storing calibration history and critical sensor information. Select the suitable electrode and calibrate it with pH buffer solutions from Mettler Toledo. Use the buffers to bracket the sample pH range. Gentle stirring the calibration solutions or samples with the U-mix magnetic stirrer ensures homogeneity and quick response. For sample measurement using InLab Surface Pro ISM, take the agar plate and simply touch the sensor tip to the media. Measure the pH of the samples. Take aliquots of the liquid media samples in a clean beaker so as to ensure that the junction is well immersed into the sample. Here are some tips and hints to ensure quick and accurate results. For thorough cleaning of the sample residues from the electrode membrane after the measurement, clean it with deionized water. Use mild soapy water or ethanol if required. After cleaning with ethanol, recondition the sensor in storage solution for two minutes. Do not rub the sensor surface. Always blot dry with tissue paper to remove any excess water. Soak the electrode in Pepsin HCL solution for one hour once in a week to remove Move protein buildup on glass membrane. Since the regular maintenance improves the life of the electrode, periodic reconditioning of the electrode is recommended. Store the electrode in in-lab storage solution when not in use. The pH range for in-lab surface pro ISM is 1 to 11 pH units and hence it should not be exposed to harsh acidic or alkaline chemicals. So, with solutions from Mettler Toledo, measuring pH of media samples is no longer a difficult task. Ensure maximum accuracy choosing the right sensor for your application.