consider purchasing your own electrode, stored in a manner (pH 4 buffer)
ready to be attached to their pH meter.  I would suggest a polypropylene
or polyethylene barrel, and a singe combination electrode.  These are 
tough, cheap and not breakable, mine lasted for years!  pH papers are
fine, with ranges in tenths, but dyes may interfer with the color change.  

Make sure it is an electrode that is compatible for TRIS buffers,
just in case you ever need to pH that type of buffer.  


Gayle Callis