# stock concentration and working concentration - (Feb/21/2011 )

If I have a powdered reagent and it says on the bottle that is 5mg. Now I want to dissolve that solution in 200 ul pbs (for example) for my experiment at a concentration of 100 ug, what we do then?
P.S. mol weight of the reagent is 1774.9

-bsp237-

100 ug per what? if you don't define the units it is pretty hard to answer your question.

5 mg = 5000 ug - if you dissolve this in 200 ul PBS you will 25 ug/ul or 25 mg/ml, you cannot get anything 100 ug out of this, unless you want to take 100 ug - in which case it is 4 ul. (c= n/v is helpful here!)

What concentration do you want for your final concentration?

-bob1-

bob1 on Mon Feb 21 23:22:44 2011 said:

100 ug per what? if you don't define the units it is pretty hard to answer your question.

5 mg = 5000 ug - if you dissolve this in 200 ul PBS you will 25 ug/ul or 25 mg/ml, you cannot get anything 100 ug out of this, unless you want to take 100 ug - in which case it is 4 ul. (c= n/v is helpful here!)

What concentration do you want for your final concentration?

what is c = n/v, can you please explain it out? thanks

-claritylight-

claritylight on Tue Feb 22 01:39:26 2011 said:

bob1 on Mon Feb 21 23:22:44 2011 said:

100 ug per what? if you don't define the units it is pretty hard to answer your question.

5 mg = 5000 ug - if you dissolve this in 200 ul PBS you will 25 ug/ul or 25 mg/ml, you cannot get anything 100 ug out of this, unless you want to take 100 ug - in which case it is 4 ul. (c= n/v is helpful here!)

What concentration do you want for your final concentration?

what is c = n/v, can you please explain it out? thanks

C is nothing more then the concentration, thus c = #moles (n) / volume (v).

-pito-

Yeah, that is the usual use, however, in the case of many things biology, c= concentration, n= the number of whatever you want (weight, total number of cells, etc.) and v=volume.

-bob1-

bob1 on Wed Feb 23 00:24:12 2011 said:

Yeah, that is the usual use, however, in the case of many things biology, c= concentration, n= the number of whatever you want (weight, total number of cells, etc.) and v=volume.

Indeed, n can mean anything really.. its just what you have in your "volume".

-pito-