I'm following a paper for their HPLC methodology, but I'm having a hard time understanding how to make mobile phase A.
To quote:
"Mobile phase A is a mixture containing 0.2% potassium dihydrogen phosphate solution and 20% tetrabutylammonium hydroxide solution (200:1, v/v)..."
I want to make a total of 500ml mobile phase solution.
My questions are:
1. How many grams or ml solution of potassium dihydrogen phosphate I should prepare?
2. How many grams or ml solution of tetrabutylammonium hydroxide I should prepare?
3. What does (200:1, v/v) mean?
Molecular weight
Potassium dihydrogen phosphate (KH2PO4): 136.09
tetrabutylammonium hydroxide (C16H37NO): 259.47
I have very little background in chemistry and this is very confusing for me. Any advice would be helpful. Thank you!
Hi.
Here is a step-by-step instructions how to make the mobile phase:
Step-1: Make 0.2% potassium dihydrogen phosphate solution.
Transfer 2.0 grams of potassium dihydrogen phosphate into a 1L volumetric cylinder or volumetric flask. Add approximately 500 mL of water. Add a stir bar and dissolve the salt (shaking can be used instead). Remove the stir bar, if used, and fill to the 1L mark with water. [optional but desired, filter through 0.45 µm or finer filter].
Step-2: 20% tetrabutylammonium hydroxide solution
Option-a) Purchase 40% tetrabutylammonium hydroxide solution in water, such as MillioporeSigma's product ID 178780. Into a vial or a beaker, mix 10.0 mL of the 40% solution with 10.0 mL of water.
Option-b) Purchase tetrabutylammonium hydroxide 30-hydrate solid (Mw~800), such as MilliporeSigma's product ID 86859. Transfer 2.96 grams of the hydrate solid into a 10 mL volumetric flask. Add a few mL of water and shake or sonicate to dissolve. Allow to cool to room temperature, if sonicated, then fill to the mark with water. [optional but desired, filter through 0.45 µm or finer filter].
The 2.96 grams accounts for the 30 water molecules present in the hydrate (if anhydrous salt is used - not sure if sold - you would need 2.0 grams instead).
Step-3: Mobile Phase-A preparation
Mix 500 mL of the 0.2% potassium dihydrogen phosphate solution from Step-1 with 2.5 mL of the 20% tetrabutylammonium hydroxide solution from Step-2. This will give you a final ratio of 200:1 v/v.
Notes:
1% solution means 1.0 gram into 100 mL. You can downscale from here to make any percent you want.
200:1 v/v means 200 parts from component-1 mixed with 1 part of compotent-2 (for example, 200 mL + 1 mL). The v/v part reads as "volume/volume".
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