Stock solutions and dilutions

[Dave0]

Hi. Newbie. First post.

 

I am hoping someone can clear something up for me.

If my stock is in w/v i.e. 100 ug/ml do I have to take my aliquot in the same unit/form i.e. w/v?

 

What happens if I did an aliquot by volume with a pippette and then made it up the desired volume. That would be v/v. Do I have to apply a conversion?

 

Please help.

 

Dave.

[studiot]

45 minutes ago, Dave0 said:

Hi. Newbie. First post.

 

I am hoping someone can clear something up for me.

If my stock is in w/v i.e. 100 ug/ml do I have to take my aliquot in the same unit/form i.e. w/v?

 

What happens if I did an aliquot by volume with a pippette and then made it up the desired volume. That would be v/v. Do I have to apply a conversion?

 

Please help.

 

Dave.

 

So is this homework or practical work or what ?

 

Unless you know the density of your solution, how would you measure it other than by volume, especially with a pipette ?

[chenbeier]

Additionally a dilution will give every time the same unit.

If Stock is mass/ volume the the dilution will also mass/ volume

Example 1g/l diluted by 10 give 0,1 g/l

If you have volume by volume then its again volume by volume.

Example 1 ml/l dilute by 2 gives 0,5ml/l

[Dave0]

Hi Chaps.

Thanks for that. I've got that squared off in my head now. I was over complicating it.

Follow up question then.

I am normally use to a stock solution expressing concentration as ug/mg and quoting its density. From which if I take a weighted aliquot (g) out of it I can convert that to ml by dividing it by the density.

I have just received a cert for a stock solution that quotes 1003ug/ml and also 997ug/g. So obviously this saves me the bother of the correction above because it is telling me from the off what is in it if I decide to do a aliquot by volume or mass anyway.

It does fail to quote the density of the solution which I don't need but I was wondering if I can work it out based on the two concentrations?

[studiot]

1 hour ago, Dave0 said:

I have just received a cert for a stock solution that quotes 1003ug/ml and also 997ug/g. So obviously this saves me the bother of the correction above because it is telling me from the off what is in it if I decide to do a aliquot by volume or mass anyway.

That will have implications for the density and actual dilution you make.

You didn't answer my earlier questions to which I would add a request for more information on what this is all about.

What is this solution and what is it for and what dilution regime are you intending to implement ?