Hi Sami,
Since this team does not support this device, I am going to move your question to the Temperature Sensor forum so that it will get the right visibility and support.
From a quick look at the application note, the LM35 will be supplying an analog voltage used for temperature compensation since the pH elctrode's output will be dependent on temperature.
Hopefully this team will be able to get you a more detailed answer shortly.
Thanks,
John