The problem with using the pH strips is that they have specific narrow ranges for the target pH, but still do not provide precise measurements under the decimal point. I would like to compare agar pH between fresh and spent media. Suggestions with low cost solutions will be appreciated. Thank you.
Setting precise pH in culture medium is crucial for growth of any organism and it should be between 5.7 - 5.8 for plant tissue cultures. pH paper strips are not suitable for determining and making precise pH in culture medium and it is advisable to invest in precision pH meters to do tissue culture experiments.
If you could gel the medium instead with Agar and use gelrite, then you could take out the plantlet or whatsoever out of the tube or dish, freeze them, and after one day you defreeze and get a luquid you can check for pH..
Freezing also works for culture medium solidified with agar. By freezing the agar (e.g. at 18°C overnight) and thawing, the agar matrix collapses and can be removed by low speed centrifugation (e.g. 5000 g for 15 min). Plenty of supernatant will be obtained for pH measurement with a regular electrode or further analysis.
Thank you for ALL of your kind responding to my question.
I think I got the answer.
S. Wenkart's answer was useful, but I am not able to altering the solidifying agent because of different mineral contents between agar and gelrite. Useful to know it.
Jean-Pierre Hernalsteens's answer:: I would like to try with your suggestion. One question might be the freezing temperature you suggested, I am sure that "-18°C", right?
Appreciated.
The freezing of the agar and its subsequent measurement sounds like a good solution. I have been asked to measure something similar in my latest manuscript. However, I have been asked to use a flat pH probe. Eventually I measured the pH of the agar using a combination of accurate pH test sticks and a pH meter on freeze/thawed agar.
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