How to make %v/v solution using a % w/v solution - (Sep/25/2014 )

Hey gang, I haven't come across this in a while, can you please solve this and show me how? I need to make a 2% v/v Ethylene imine polymer in buffered solution using a 50% w/v solution of Ethylene imine polymer in water. I'm going to pull the last remaining hairs out if I don't stop staring at this. It's for crystallization buffers. Thanks!!

 

The directions from Hampton Research do not specify what stock solution of PEI to use, so I'm hoping that they mean the stock solution that they sell which is 50% w/v and I use that to create a 2% v/v.

 

2 ml of 50 % w/v PEI

brought up to 10 ml final volume

 

Coming across some really whacky buffer requirements today, this is just the start of a very loooooooooooooooong day

2% v/v from 50% w/v? strange.

 

2% of a 50% solution would be 2 ml in a final volume of 100 ml (1% w/v final).

 

but, if you want 2% w/v then you would use 4 ml in a final volume of 100 ml (which i think may be more likely the case)

yes, you need to take 4ml from the 50% solution.

And add till you have 100ml.

 

this seems the correct way, but its a strange thing to be honest.

I honestly don't know why certain manufacturers are so frigging cryptic about their protocols. Who the hell talks like that ???

 

Thank you both so very much, I think we have multiple correct answers here, I'm calling Tech support and ask them WTH do they mean to say????

 

I'll let you know what they say.

Have a great weekend !!!

The way how I see it:

 

2% v/v means: 2 ml of a 100% solution. (liquid).

 

So you need 2ml of a 100% PEI liquid.

 

You have a 50% w/V , meaning: 50 grams in 100ml... while you need 100%, so you just take 4 ml rather than 2ml

DING DING DING!!!!!

 

Pito and mdfenko get the whole box of gold stars!!! I love you folks!!! It's been the brain burn week from hell, I couldn't even remember my SS# to give one of my PI's for an NIH grant update. I just couldn't get my brain to think this through. You guys ROCK!! I know we've all had those moments where we stare at numbers and they just stare back at us, this was one of those times. Thank you, it's been making me crazier. You've made it crystal clear for me. Man, I really hate brain farts!!!!!!! Have an awesome weekend!!!!

 

Here's the question and answer from Hampton Research

 

Yes, a 2% v/v solution could be formulated from 50% w/v Ethylene imine.  For example, to make 10 ml of Crystal Screen HT reagent Crystal Screen 2 #16 / Crystal Screen HT F4 0.5 M Sodium chloride, 0.1 M Sodium citrate tribasic dihydrate pH 5.6, 2% v/v Ethylene imine polymer:

 

7.6 ml Deionized water (less in order to adjust pH – see below)

0.4 ml 50% Ethylene imine polymer (HR2-599)

1ml 5.0 M Sodium chloride (HR2-637)

1.0 ml 1.0 M Sodium citrate tribasic dihydrate pH 5.6 (HR2-735)

 

If you make your own Sodium citrate tribasic dihydrate buffer, use HCl to adjust the pH.

 

Note:  Ethylene imine is very basic, about pH 12.  You will need to titrate this reagent after formulation to pH 5.6 using HCl.  If you were to make 10 ml you would need to add about 250ul of concentrated HCl and then fine tune the pH using 1.0 M HCl to pH 5.6.

 

You can order this reagent separately as HR2-912-16 Crystal Screen 2 #16 / Crystal Screen HT F4 185ml 0.5 M Sodium chloride, 0.1 M Sodium citrate tribasic dihydrate pH 5.6, 2% v/v Ethylene imine polymer $152.00

 

Let me know if you have any other questions.  Hope this made it in time to save your hair.

 

 

 

Hello,

 

There's is some confusion in the buffer listed on the HR2-110 screen, 

 

Well ID F4

 

is listed as having 2% v/v Ethylene imine polymer (PEI). The only stock solutions that I find for sale are 50% w/v. Am I to assume that this is the stock solution from which to make the 2% v/vworking solution?

 

Please advise while I still have hair left...   ​

 

Best,