pH calc for use in HPLC mobile phases

[chembot]

Perhaps, I dont have the info (pka values) for this but am looking for process of calculating (and the pH value) pH for the following solutions:

23mM NaOH+7mM Na2B4O7

80mM NaOH+18mM Na2B4O7

400mM NaOAc+1mM NaOH

530mM NaOH + 650mM H3BO3

23mM NaOH + 7mM NaH2BO3

80mM NaOH + 23mM NaH2BO3

1mM NaOH + 300mM H3BO3

Ive calculated pH values for the above myself but am not sure if I'm going through the process correctly and have the correct values. Any help with this is appreciated.

Thanks.

[Bill Tindall]

to calculate the pH correctly you will need to use activity coefficients. the following link will provide these calculations
Vhttp://www.bi.umist.ac.uk/users/mjfrbn/buffers/Makebuf.asp

Unless they have updated the site, the Zirchrom site does not use activity corrections and you will not get the correct answer with this site.

I am curious, why do you need to know what the pH of these solutions are?

[chembot]

The reason why I need these values is to ascertain whether or not the pH values are outside of the workable pH range of my SAX column. I am doing pH gradients of aa's and these buffers, ionic solutions are reported in the literature for such separations. I just want to make sure I'm not ruining my column since some of these are pH 13. Then again, my pH calculations are a little rusty and thus, the reason for the posted msg.

Any help is greatly appreciated.

chembot