increasing or reducing pH of buffers when I am adding MQ water

sudheer sangeetham via (by sudheer.pbm07 from
Thu Mar 8 08:32:22 EST 2012

I am preparing 10X PBS, 100 ml, the recipe is nacl - 8 g, kcl - 2g, na2hpo4
- 0.14 g , k2hpo4 - 0.027 g. Initially I dissolved these chemicals in 50ml
of mq , this time ph was 6.3, when I added 25 ml mq to this, it has shown
ph 7.2  I wondered what is happening?

Then I check the 10x sds running buffer ph, it has shown ph 8.65, when I
made this to 1x , it has shown 8.0.

Then I thought problem with my mq water, then i check the ph of it, it has
shown ph 5.6. As I remember the mq water ph 7 or 6.8.  I read some of the
forums, I came to know that H2o reacts with co2 in the air and forms
carbonic acid, may be because of this my mq water ph 5.6.

Could any body tell me any soultion? How to degas co2 from mq water?

Thank you in advance.

Sudheer Babu.S
Ph.D student
Institute of Biochemistry
Biological Research Center

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