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I have a basic question on a reagent (solution) preparation. Here are the steps that I take to prepare the reagent:

  1. Weigh the chemical (solid form, ammonium bicarbonate) and dissolve with DW to make 100 mM solution. The weight (or volume needed to make 100 mM) can vary depending on the # of the samples to be analyzed

  2. Calibrate the pH meter and adjust the pH of the above solution to a certain pH

I would like to make my life easier by not using the pH meter (gets tedious having to wait for the pH calibration and whatnot). I do know that theoretically, if I make the weight of the chemical the same each time I prepare the solution, I can add the same amount of base to set the pH. But is it correct that the volume of base added changes depending on the amount of chemical weighed?

I don't remember my chemistry very well, but from my memory, pH is concentration dependent so I was wondering if adding the same volume of base to a solution of desired concentration (but may have different volumes as I may weigh the chemical differently) is reproducible.

So basically, I want to simply weigh the chemical, dissolve with required volume of DW to make 100 mM concentration, and then add the same volume of base without having to use my pH meter, which will save a lot of time in the morning.

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    $\begingroup$ Why not to note the particular volume ratio for the used base or acid neutralization solution and the 100 mM NH4HCO3 solution ? Then you can repeat it without pH measurement. E.g.illustratively, for 100 mL of 100 mM NH4HCO3 you spend 1.23 mL of 1 M acid/base. Then you use 100/1.23 mL ratio all the time, occasionally check if all is as expected. $\endgroup$
    – Poutnik
    Dec 7, 2022 at 11:46
  • $\begingroup$ Oh yeah wow I completely forgot about using the ratio!! Thank you!! $\endgroup$
    – user129533
    Dec 7, 2022 at 15:11

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