User Guide and Calibration Manual for the Buffer Solution 465 mv: Exchanges and Tips

Hello, I bought a 465 mv Calibration Buffer Solution last August and again in March when I went to calibrate my probe, I noticed that the measurements from the two bottles were not the same. I thought maybe it's because the one from August had already been opened, is that the case? Is there a time limit for using the bottle once it's been opened?
Best regards,
Christian

Hello,
What is the difference?

About 20mv.
So, I have some doubt about which bottle is accurate.

That's not very significant, it's possible that one of the bottles has been slightly contaminated.

Before inserting the probe into the bottle, should I rinse it with demineralized water?

Yes. Take the last bottle as a reference, as it should be the least contaminated.

Perfect, thank you very much. Have a nice day.

Have a nice day.