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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: blackjacktam on March 21, 2017, 10:07:27 PM

Title: How to make the concentration of PSS and PEI solutions
Post by: blackjacktam on March 21, 2017, 10:07:27 PM

Dear all,

We have purchased polyethyleneimine (PEI, Mw=70 000g/mol, 30 wt%) and Poly(sodium 4-stryrene sulfonate) (PSS, Mw=10 000g/mol, 25 wt%). We want to make a concentration of 30 mg/mL on polyelectrolyte PSS and 13.5mg/mL on PEI solution, but we don't know how to make it. Pls help how to do it in step by step. Thanks a lot!

Title: Re: How to make the concentration of PSS and PEI solutions
Post by: Hunter2 on March 22, 2017, 10:59:17 AM

You know the final content. Mass divided by volume. You know the percentage of the components. So you calculate to 100%

In case of PSS you have to weight 4 times of the mass you want to have and for PEI 3.33 times .

Title: Re: How to make the concentration of PSS and PEI solutions
Post by: Enthalpy on March 23, 2017, 10:39:51 AM

Here's an example for PEI. Adapt it to PSS - I suppose two distinct solutions.

Weigh 1g of 30 wt% solution of PEI. The volume differs from 1cm³ since the solution isn't pure water at +4°C. It contains 0.3g of PEI. You want 13.5g/L so the final volume must be 0.3/13.5=22.2cm³. Add the necessary solvent amount to attain this volume.

Depending on the desired amount of solution, scale up or down both figures identically: 1g and 22.2cm³.

You have to measure a mass and a volume here because you go from a wt% concentration to a g/L one and the density of solvents and solutions isn't in the data you provide.

I can't tell the exact procedure for mixing. Sometimes there are subtleties, for instance with thick solutions, and sometimes it's as simple as sugar in coffee.