There is some impurity in the NaOH we used in the QA lab, therefore we always “calibrated” a carboy of alkali for titrations using salicylic acid and weighing to 0.001 gram. Yes carboys, so we had a CO2 trap on the bung since it reacts with alkali.
For home use, your standard error is one drop/ roughly 0.05 gram of solution. For home use the working goal is 0.5 to 0.7% TA. Using a reagent grade NaOH pellet and ignoring the contaminant is good enough for estimated error. ,,,,, Grandpa never had any chemistry and could make acceptable wine. ,,,, My look at running TA is that it gives a reference point on where you are versus the rest of the world of wine. The exact number doesn’t matter as much as understanding what direction tastes are coming from. ,,,, I sin comming from a lab background. There are folks in the Vinters club who are better wine makers than me because they can taste the changes in real time.
I would guess the pH probe/ meter has more to do with a measured pH of 12.9 than the reagent and distilled water. ,,,, humm have I ever measured anything that was 14.0? ,,, , , , NO! ,,, 14 is a theoretical number saying ten to the 14th power. Likewise I have never measured a pH of 0