I bought mine used I would try it. water is usually 7.0

just soak it in water(I don't think you need that solution)...I store some water in cap to keep electrode filter wet. I would ask a hydro shop guy...I am sorry...I know I recommended that pen, but I got mine used off ebay 1-1/2 years ago and never have used the calibration solution...It came calibrated. let me know if this helps...If not I will look into it, by asking a hydro store friend...peace
p.s. I have dropped mine and all kinds of stuff...It has held up over time, and my hydro store have totally switched to milwaukee after having alot of service problems with Hanna...