You can use a pH meter to measure pD values however an adjustment factor is needed.  If you calibrate your pH meter using standard solutions in H2O you need to add 0.4 to get the correct value.  For example if you are measuring the pD of a D2O solution and your meter says pH 7 the actual pD is 7.4, thus if you were aiming for a pD 7 solution to should adjust with DCl/NaOD until the meter says 6.6.

i.e. pD = pH* + 0.4 , where pH* is the observed value 

DCl can easily be prepared by adding oxalyl chloride to (carefully) D2O bearing in mind that 1eq of oxalyl chloride gives 2eq of acid.

For NaOD add sodium metal to D2O (again very carefully!)

Hope this helps!

You can use a pH meter to measure pD values however an adjustment factor is needed.  If you calibrate your pH meter using standard solutions in H2O you need to add 0.4 to get the correct value.  For example if you are measuring the pD of a D2O solution and your meter says pH 7 the actual pD is 7.4, thus if you were aiming for a pD 7 solution to should adjust with DCl/NaOD until the meter says 6.6.

i.e. pD = pH* + 0.4 , where pH* is the observed value 

DCl can easily be prepared by adding oxalyl chloride to (carefully) D2O bearing in mind that 1eq of oxalyl chloride gives 2eq of acid.

For NaOD add sodium metal to D2O (again very carefully!)

Hope this helps!

Dear Shaun Stairs.

Thank you very much for your reply. Your answer does help. I think I haven't made this question clear enough. For a normal electrode on a pH meter, only 0.5 mL of D2O might be not enough to get the value. 

Do we need to change our common eletrode to a special, mini eletrode that we could put it into the NMR tube

Use DCl, NaOD and CD3COOD

in different proprtions

Sorry for the confusion.  In my lab we use a small probe with a diameter of 6mm (see link for example).  This fits nicely into a 2ml eppendorf tube and allows us to pH as little as 400uL.  If you haven't got a probe this small I think you'll struggle unless you've got plenty of material and D2O to waste making larger stock solutions.

http://us.mt.com/us/en/home/products/Laboratory_Analytics_Browse/pH/sensor_electrode/ph_electrodes_family_page/InLab_special_electrodes_family_page/InLab_Semi-Micro_1.html